A preparation method of Z-mechanism CoP3 / CdZnS lawsonia inermis p-n heterojunction photocatalytic material

Abstract

The application discloses a preparation method of Z-mechanism CoP3 / CdZnS p-n heterojunction photocatalytic material, and the method comprises the following steps: preparing a CdZnS in a closed system by a solvothermal method, and further preparing a CoP3 / CdZnS p-n heterojunction with a Z-mechanism by a hydrothermal method. The p-n heterojunction is a CdZnS with a nanorod structure and modified by CoP3 quantum dots, forms numerous micro heterojunction interfaces, has a Z-mechanism photocatalytic mechanism, and the obtained CdZnS with a lawsonia inermis shape is composed of CdZnS nanorods with dislocation defects. The CoP3 / CdZnS photocatalytic material is used for photocatalytic hydrogen production, has a high hydrogen production rate, is used for photocatalytic oxidation degradation of H2S, drugs and organic dyes in an aqueous solution, has a good photocatalytic stability, and is used for photocatalytic oxidation degradation of H2S, drugs and organic dyes in an aqueous solution.

Description

Technical Field

[0001] This invention belongs to the field of new energy and environmental protection, and relates to a method for preparing a Z-mechanism CoP3 / CdZnS pn heterojunction. Specifically, it relates to a method for preparing a pn heterojunction photocatalytic material formed by CoP3 quantum dot-modified CdZnS with dislocation defects; further, it relates to a method for preparing a Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material. Background Technology

[0002] As a sustainable resource, the efficient use of solar energy can alleviate current energy and environmental problems. Semiconductor-based photocatalysis is considered a promising strategy for converting solar energy into chemical energy.

[0003] In recent years, Cd x Zn 1-x CdZnS has been extensively studied due to its ease of modulation, resistance to photocorrosion, and strong visible light response. Compared to CdZnS nanoparticle structures, one-dimensional CdZnS nanostructures provide channels for electron migration and promote the rapid migration of photogenerated carriers. Assembling one-dimensional CdZnS nanostructures into hierarchical structures can further enhance light absorption; however, the photocatalytic activity of standalone CdZnS remains very low. Therefore, designing and constructing highly efficient photocatalyst materials still faces significant challenges.

[0004] The construction of heterostructures is one of the effective strategies to further improve the catalytic performance of catalytic materials. The presence of heterojunctions not only provides more active sites for photocatalytic reactions but also helps to promote the separation of photogenerated electron-hole pairs and improve the charge transfer rate. Among various types of heterojunctions, p-type photocatalytic materials and n-type semiconductor photocatalytic materials forming pn junctions have attracted widespread attention due to their large Fermi level potential difference, which can generate a strong internal electric field in the heterojunction. However, the type II carrier migration method leads to a decrease in the redox potential of photoinduced hole-electron pairs, and the presence of photogenerated electrons and holes in photocatalytic materials inhibits the interfacial transfer of electrons and holes in other catalytic materials, thus limiting its application. Therefore, the Z-type mechanism has a special transfer pathway and retains strong oxidation and reduction, which is more conducive to the separation and transfer of electrons and holes. Constructing Z-type mechanism pn heterojunctions will be beneficial to the further development of photocatalytic materials. However, the preparation of Z-type pn heterojunctions still faces great challenges, with complicated processes, limited active sites, and poor interfacial coupling, which restricts their commercial application in photocatalytic water splitting.

[0005] For the reasons mentioned above, the key problem to be solved by this invention is to find a simple preparation process that can produce Z-mechanism CoP3 / CdZnS pn heterojunctions with high active sites and significant catalytic performance and stability. Summary of the Invention:

[0006] The purpose of this invention is to provide a method for preparing a Z-mechanism CoP3 / CdZnS sycamore fruit-shaped pn heterojunction photocatalytic material. Addressing the shortcomings of existing technologies in preparing CoP3 / CdZnS heterojunction photocatalytic materials, such as cumbersome processes, limited active sites, poor interfacial coupling, and low catalytic activity, this invention proposes a Z-mechanism method for preparing a sycamore fruit-shaped pn heterojunction photocatalytic material. The method is characterized in that the pn heterojunction is composed of n-type CdZnS nanobuilding units modified with p-type CoP3 quantum dots, forming a CoP3 / CdZnS pn heterojunction. The CdZnS nanobuilding units possess dislocation defect structures, and the CoP3 quantum dot modification on the surface of the CdZnS nanobuilding units can form numerous tiny heterojunction interfaces. The CoP3 / CdZnS pn heterojunction nanobuilding units self-assemble into a sycamore fruit-shaped spherical self-assembled body. The photocatalytic material exhibits a Z-mechanism photocatalytic mechanism. The preparation method specifically includes the following steps:

[0007] (1) Dissolve 1-10 mmol Cd(NO3)2·4H2O, 1-10 mmol Zn(NO3)2·6H2O, and 1-50 mmol thiourea in 10-200 ml water and 10-200 ml ethylenediamine, stir for 30 min, transfer to a 50-500 ml autoclave, place in an oven at 100-220℃ and react for 3-24 h, remove, cool naturally to room temperature, centrifuge and dry to obtain a light yellow sycamore fruit-shaped CdZnS sample with dislocation defects;

[0008] (2) Weigh 0.1-5.0g of CdZnS sample obtained in step (1) and disperse it in water. Add 0.1-2.0g of NaH2PO2, 0.01-2.0g of CoCl2·6H2O, and 0.1-2.0g of NaBH4 and dissolve them in 35-400mL of deionized water. Stir for 30min, transfer to a 50-500mL stainless steel autoclave lined with polytetrafluoroethylene, and react at 100-220℃ for 3-24h. Allow it to cool naturally to room temperature, centrifuge and dry to obtain the sycamore fruit-shaped CoP3 / CdZnS pn heterojunction photocatalytic material.

[0009] The advantages of this invention are as follows: a simple hydrothermal method was used to synthesize a sycamore-fruit-shaped CdZnS photocatalytic material composed of CoP3 quantum dots. The small particle size facilitates rapid charge separation and transfer within the quantum dots. After growing CoP3 quantum dots on a one-dimensional nanostructured CdZnS, a pn heterojunction interface is generated, forming a space charge region. This leads to electron transfer along a specific path, promoting photogenerated carrier separation, inhibiting electron-hole recombination, and improving photocatalytic hydrogen production activity. Simultaneously, the Z-shaped transfer mechanism also facilitates rapid electron-hole pair separation and transfer. The unique nanostructure composed of sycamore-fruit-like structures also provides a high specific surface area and more active sites for the reaction. This improves the catalytic activity and stability of the material, contributing to rapid interfacial charge transfer and enhanced long-term operational stability. It can be used for efficient photocatalytic water splitting to produce hydrogen and oxygen; it can also be used for photocatalytic oxidation of harmful gases such as formaldehyde, nitrogen oxides, and H2S; and it can also photocatalytically degrade organic dyes and organic pollutants such as pharmaceuticals in wastewater. Attached Figure Description

[0010] Figure 1 The X-ray powder diffraction (XRD) spectra of the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared by the method described in Example 1 of this invention, and the photocatalytic materials of Comparative Example 1 and Comparative Example 2.

[0011] Figure 2 The image shows a scanning electron microscope (SEM) image of the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared using the method described in Example 1 of this invention.

[0012] Figure 3 These are transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM) images of the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared using the method described in Example 1 of this invention.

[0013] Figure 4 STEM-ADF images and corresponding elemental distribution diagrams of the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared using the method described in Example 1 of this invention.

[0014] Figure 5 The results show the UV-Vis absorption performance of the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared by the method described in Example 1 of this invention, and the photocatalytic materials of Comparative Example 1 and Comparative Example 2.

[0015] Figure 6The XPS test results are for the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared by the method described in Example 1 of this invention, and for the photocatalytic materials of Comparative Example 1 and Comparative Example 2.

[0016] Figure 7 The results of the Mott-Schottky curves for the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared by the method described in Example 1 of this invention, and the photocatalytic materials of Comparative Example 1 and Comparative Example 2 are shown.

[0017] Figure 8 The results of the free radical capture experiments of the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared by the method described in Example 1 of this invention and the DMPO free radical capture experiments of the photocatalytic materials of Comparative Example 1 and Comparative Example 2 are presented.

[0018] Figure 9 The results show the photocatalytic hydrogen production performance of the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared by the method described in Example 1 of this invention, and the photocatalytic materials of Comparative Example 1 and Comparative Example 2.

[0019] Figure 10 The results show the stability of photocatalytic hydrogen production of the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared by the method described in Example 1 of this invention. Detailed Implementation

[0020] Example 1:

[0021] (1) Dissolve 1.8 mmol Cd(NO3)2·4H2O, 1.2 mmol Zn(NO3)2·6H2O, and 9.0 mmol thiourea in 10 ml water and 20 ml ethylenediamine, stir for 30 min, transfer to a 50 ml autoclave, place in an oven at 180 ℃ and react for 12 h, remove, cool naturally to room temperature, centrifuge and dry to obtain a light yellow sycamore fruit-shaped CdZnS sample with dislocation defects;

[0022] (2) Weigh 0.5g of CdZnS sample obtained in step (1) and disperse it in water. Add 0.2g of NaH2PO2, 0.04g of CoCl2·6H2O and 0.2g of NaBH4 and dissolve them in 35mL of deionized water. Stir for 30min, transfer to a 50mL stainless steel autoclave lined with polytetrafluoroethylene, and react at 180℃ for 8h. Cool naturally to room temperature, centrifuge and dry to obtain yellow-green sycamore fruit-shaped CoP3 / CdZnS pn heterojunction photocatalytic material.

[0023] Example 2:

[0024] (1) Dissolve 1.8 mmol Cd(NO3)2·4H2O, 1.2 mmol Zn(NO3)2·6H2O, and 9.0 mmol thiourea in 150 ml water and 15 ml ethylenediamine, stir for 30 min, transfer to a 50 ml autoclave, place in an oven at 180 ℃ for 12 h, remove, cool naturally to room temperature, centrifuge and dry to obtain a light yellow sycamore fruit-shaped CdZnS sample with dislocation defects;

[0025] (2) Weigh 0.5g of CdZnS sample obtained in step (1) and disperse it in water. Add 0.2g NaH2PO2, 0.02g CoCl2·6H2O and 0.2g NaBH4 and dissolve them in 35mL of deionized water. Stir for 30min, transfer to a 50mL stainless steel autoclave lined with polytetrafluoroethylene, and react at 100℃ for 24h. Cool naturally to room temperature, centrifuge and dry to obtain yellow-green sycamore fruit-shaped CoP3 / CdZnS pn heterojunction photocatalytic material.

[0026] Example 3:

[0027] (1) Dissolve 1.8 mmol Cd(NO3)2·4H2O, 1.2 mmol Zn(NO3)2·6H2O, and 9.0 mmol thiourea in 20 ml water and 10 ml ethylenediamine, stir for 30 min, transfer to a 50 ml autoclave, place in a 220 ℃ oven for 6 h, remove, cool naturally to room temperature, centrifuge and dry to obtain a light yellow sycamore fruit-shaped CdZnS sample with dislocation defects;

[0028] (2) Weigh 0.5g of CdZnS sample obtained in step (1) and disperse it in water. Add 0.2g of NaH2PO2, 0.08g of CoCl2·6H2O and 0.2g of NaBH4 and dissolve them in 35mL of deionized water. Stir for 30min, transfer to a 50mL stainless steel autoclave lined with polytetrafluoroethylene, and react at 220℃ for 6h. Cool naturally to room temperature, centrifuge and dry to obtain yellow-green sycamore fruit-shaped CoP3 / CdZnS pn heterojunction photocatalytic material.

[0029] Example 3:

[0030] (1) Dissolve 1 mmol Cd(NO3)2·4H2O, 1 mmol Zn(NO3)2·6H2O, and 1 mmol thiourea in 10 ml water and 10 ml ethylenediamine, stir for 30 min, transfer to a 50 ml autoclave, place in a 100 ℃ oven for 3 h, remove, cool naturally to room temperature, centrifuge and dry to obtain a light yellow sycamore fruit-shaped CdZnS sample with dislocation defects;

[0031] (2) Weigh 0.1g of CdZnS sample obtained in step (1) and disperse it in water. Add 0.1g of NaH2PO2, 0.01g of CoCl2·6H2O and 0.1g of NaBH4 and dissolve them in 35mL of deionized water. Stir for 30min, transfer to a 50mL stainless steel autoclave lined with polytetrafluoroethylene, and react at 220℃ for 3h. Cool naturally to room temperature, centrifuge and dry to obtain yellow-green sycamore fruit-shaped CoP3 / CdZnS pn heterojunction photocatalytic material.

[0032] Example 4:

[0033] (1) Dissolve 10 mmol Cd(NO3)2·4H2O, 10 mmol Zn(NO3)2·6H2O, and 50 mmol thiourea in 200 ml water and 200 ml ethylenediamine, stir for 30 min, transfer to a 500 ml autoclave, place in an oven at 180 ℃ for 6 h, remove, cool naturally to room temperature, centrifuge and dry to obtain a light yellow sycamore fruit-shaped CdZnS sample with dislocation defects;

[0034] (2) Weigh 5.0g of CdZnS sample obtained in step (1) and disperse it in water. Add 2.0g of NaH2PO2, 2.0g of CoCl2·6H2O and 2.0g of NaBH4 and dissolve them in 400mL of deionized water. Stir for 30min, transfer to a 500mL stainless steel autoclave lined with polytetrafluoroethylene, and react at 180℃ for 6h. Cool naturally to room temperature, centrifuge and dry to obtain yellow-green sycamore fruit-shaped CoP3 / CdZnS pn heterojunction photocatalytic material.

[0035] Example 5:

[0036] (1) Dissolve 10 mmol Cd(NO3)2·4H2O, 10 mmol Zn(NO3)2·6H2O, and 50 mmol thiourea in 50 ml water and 150 ml ethylenediamine, stir for 30 min, transfer to a 250 ml autoclave, place in a 220 ℃ oven and react for 3 h, remove, cool naturally to room temperature, centrifuge and dry to obtain a light yellow sycamore fruit-shaped CdZnS sample with dislocation defects;

[0037] (2) Weigh 5.0g of CdZnS sample obtained in step (1) and disperse it in water. Add 2.0g of NaH2PO2, 2.0g of CoCl2·6H2O and 2.0g of NaBH4 and dissolve them in 200mL of deionized water. Stir for 30min, transfer to a 250mL stainless steel autoclave lined with polytetrafluoroethylene, and react at 220℃ for 3h. Cool naturally to room temperature, centrifuge and dry to obtain yellow-green sycamore fruit-shaped CoP3 / CdZnS pn heterojunction photocatalytic material.

[0038] Example 6:

[0039] (1) Dissolve 5 mmol Cd(NO3)2·4H2O, 10 mmol Zn(NO3)2·6H2O, and 30 mmol thiourea in 150 ml water and 50 ml ethylenediamine, stir for 30 min, transfer to a 300 ml autoclave, place in an oven at 150 °C and react for 12 h, remove, cool naturally to room temperature, centrifuge and dry to obtain a light yellow sycamore fruit-shaped CdZnS sample with dislocation defects;

[0040] (2) Weigh 5.0g of CdZnS sample obtained in step (1) and disperse it in water. Add 2.0g of NaH2PO2, 1.0g of CoCl2·6H2O and 1.0g of NaBH4 and dissolve them in 200mL of deionized water. Stir for 30min, transfer to a 300mL stainless steel autoclave lined with polytetrafluoroethylene, and react at 150℃ for 8h. Cool naturally to room temperature, centrifuge and dry to obtain yellow-green tung-fruit-like CoP3 / CdZnS pn heterojunction photocatalytic material.

[0041] Example 7:

[0042] (1) Dissolve 10 mmol Cd(NO3)2·4H2O, 5 mmol Zn(NO3)2·6H2O, and 30 mmol thiourea in 100 ml water and 50 ml ethylenediamine, stir for 30 min, transfer to a 200 ml autoclave, place in an oven at 180 ℃ for 6 h, remove, cool naturally to room temperature, centrifuge and dry to obtain a light yellow sycamore fruit-shaped CdZnS sample with dislocation defects;

[0043] (2) Weigh 3.0g of CdZnS sample obtained in step (1) and disperse it in water. Add 1.0g of NaH2PO2, 0.5g of CoCl2·6H2O and 0.5g of NaBH4 and dissolve them in 150mL of deionized water. Stir for 30min, transfer to a 200mL stainless steel autoclave lined with polytetrafluoroethylene, and react at 180℃ for 6h. Cool naturally to room temperature, centrifuge and dry to obtain the sycamore fruit-shaped CoP3 / CdZnS pn heterojunction photocatalytic material.

[0044] Comparative Example 1:

[0045] 1.8 mmol Cd(NO3)2·4H2O, 1.2 mmol Zn(NO3)2·6H2O, and 9.0 mmol thiourea were dissolved in 10 ml water and 20 ml ethylenediamine. The mixture was stirred for 30 min, transferred to a 50 ml autoclave, and placed in an oven at 180 °C for 12 h. After being removed and allowed to cool naturally to room temperature, the mixture was centrifuged and dried to obtain a light yellow, sycamore-fruit-shaped CdZnS sample with dislocation defects.

[0046] Comparative Example 2:

[0047] Weigh 0.2g NaH2PO2, 0.04g CoCl2·6H2O, and 0.2g NaBH4 and dissolve them in 35mL of deionized water. Stir for 30 minutes, transfer to a 50mL stainless steel autoclave lined with polytetrafluoroethylene, and react at 180℃ for 8 hours. After naturally cooling to room temperature, centrifuge and dry to obtain CoP3 quantum dot samples.

[0048] Figure 1 X-ray powder diffraction (XRD) patterns of the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared by the method described in Example 1 of this invention, and the photocatalytic materials of Comparative Examples 1 and 2. From the XRD pattern in pattern a, it can be seen that the characteristic peaks of CdS and ZnS match well with the characteristic peaks of ZnS (PDF#36-1450) and CdS (PDP#77-2306). The diffraction peaks of CdS and ZnS have shifted, proving that the prepared catalytic material is not a mixture of cadmium sulfide and zinc sulfide, but a CdZnS solid solution. The diffraction peaks of the CoP3 / CdZnS sample in Example 1 are the same as those of the CdZnS sample in Comparative Example 1. Clearly, the pattern shows the highest intensity of the (002) peak, indicating that the CdZnS nanostructure is oriented along the <001> axis. The absence of the CoP3 peak can be attributed to low CoP3 loading or high dispersion. The characteristic peaks of the XRD pattern of CoP3 in Comparative Example 2 in Figure b match well with the standard card (PDF#73-1239), and the two distinct characteristic peaks correspond to the (200) and (321) crystal planes of CoP3. The presence of CoP3 in the composite catalytic material can be confirmed by subsequent TEM and XPS analyses.

[0049] Figure 2The images show scanning electron microscope (SEM) images of the Z-mechanism CoP3 / CdZnS pn heterojunction photocatalytic material prepared using the method described in Example 1 of this invention. Low-magnification image a shows that the obtained Z-mechanism CoP3 / CdZnS pn heterojunction appears as sycamore-fruit-shaped microspheres. High-magnification image b shows that the obtained sycamore-fruit-shaped CoP3 / CdZnS microspheres are composed of one-dimensional nanostructures with a length and diameter of approximately 200 nm and 30 nm, respectively. This structure enhances light absorption. The Z-mechanism CoP3 / CdZnSp-n heterojunction facilitates electron-hole separation, improves redox capacity, and thus enhances photocatalytic performance.

[0050] Figure 3 The images show transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) images of the Z-mechanism CoP3 / CdZnS pn heterojunction photocatalytic material prepared using the method described in Example 1 of this invention. Figure a shows the TEM image, which reveals that the Z-mechanism CoP3 / CdZnS pn heterojunction is composed of microspheres assembled from one-dimensional nanostructures. Figure b shows the HRTEM image, which indicates that the one-dimensional CdZnS nanostructures possess dislocation defects and are uniformly loaded with CoP3 quantum dots, forming numerous tiny heterojunction interfaces. The 0.33 nm lattice fringes correspond to the (002) crystal surface of CdZnS, indicating the directional growth of the one-dimensional CdZnS nanostructures along the <001> axis. The HRTEM results are consistent with the XRD results. The 0.24 nm lattice fringes correspond to the (321) crystal surface of CoP3. This clearly shows that the CoP3 quantum dots are uniformly distributed on the CdZnS surface. HRTEM images clearly confirm that CoP3 forms a tight interfacial coupling with the CdZnS plane, which promotes the rapid migration of photocarriers from CdZnS to CoP3, thereby improving charge separation efficiency.

[0051] Figure 4 The images show STEM-ADF photographs and corresponding elemental distribution maps of the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared using the method described in Example 1 of this invention. The ADF photographs and corresponding elemental distribution maps of Cd, Zn, S, Co, and P show that Co and P elements are uniformly distributed on the CdZnS surface, further indicating that CoP3 quantum dots have been successfully composited on the one-dimensional nanostructure CdZnS.

[0052] Figure 5The results show the UV-Vis absorption performance of the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared using the method described in Example 1 of this invention, and the photocatalytic materials of Comparative Examples 1 and 2. Comparative Example 2, CoP3, shows almost a straight line with high adsorption capacity across the entire UV-Vis wavelength range, which may be related to its narrow band gap and black color. Comparative Example 1, CdZnS, exhibits strong light absorption capacity. Coupling with CdZnS increases the visible light absorption of the composite material. Furthermore, the heterostructure formed between CdZnS and CoP3 leads to a redshift in the light absorption of the composite material. UV-Vis spectral analysis concludes that the composite catalytic material has stronger visible light absorption capacity, can utilize more photons, and is beneficial for promoting photocurrent response.

[0053] Figure 6 The XPS test results are shown for the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared by the method described in Example 1 of this invention, and for the photocatalytic materials of Comparative Examples 1 and 2. In the XPS spectrum of Cd3d (Figure a), the positions of the two binding energy peaks are 404.3 eV and 411.2 eV, respectively, corresponding to Cd 2+ In the XPS spectrum of Zn2p (Figure b), the two binding energy peaks are located at 1021.4 eV and 1044.3 eV, respectively, corresponding to Zn 2+ The binding energy peak positions of Cd and Zn did not change significantly. In the 2p mode of S in CdZnS (Figure c), the positions of the two binding energy peaks are 160.5 eV and 161.8 eV, respectively, belonging to S. 2- 2p 3 / 2 and 2p 1 / 2 After CoP3 is composited into CdZnS, the binding energy of Cd, Zn, and S in the composite material exhibits a higher energy change compared to the original composite. The difference in binding energy is due to the surface electron density. The Co2p XPS spectrum shown in Figure d can be divided into four binding energy peaks. The binding energy peaks at 795.95 eV and 780.15 eV are Co2p1 / 2 and Co2p3 / 2, respectively, while the peaks at 784.85 eV and 801.95 eV are satellite peaks. As shown in Figure e, the P2p peaks at 130.15 eV and 128.95 eV are similar to the P2p peaks in CoP3. 1 / 2 and P 2p 3 / 2Consistent. According to XPS analysis, the change in binding energy can be attributed to the difference in electron concentration caused by electron transfer and close interface interactions. Due to the construction of the CoP3 / CdZnS heterojunction, electrons transfer from CdZnS to CoP3, establishing a new Fermi level equilibrium. Simultaneously, an internal space charge field is generated at the interface of the prepared CoP3 / CdZnS heterojunction, which promotes the separation of photogenerated carriers, facilitating the Z-mechanism transfer pathway with high redox capacity, thereby enhancing photocatalytic activity.

[0054] Figure 7 The Mott-Schottky curves of the Z-mechanism CoP3 / CdZnS sycamore-like pn heterojunction photocatalytic material prepared using the method described in Example 1 of this invention, and the photocatalytic materials of Comparative Examples 1 and 2 are shown. In Figure b, the slope of Comparative Example 1 CdZnS is positive, indicating it is an n-type semiconductor. In Figure c, the slope of Comparative Example 2 CoP3 is negative, indicating it is a p-type semiconductor. The Mott-Schottky diagram of CoP3 / CdZnS in Figure a clearly shows an inverted "V" shape, proving that CoP3 / CdZnS is a pn heterojunction.

[0055] Figure 8 The results of free radical scavenging experiments using the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared by the method described in Example 1 of this invention, and the DMPO free radical scavenging results of the photocatalytic materials of Comparative Examples 1 and 2 are presented. 5,5-Dimethyl-1-pyrrolline-N-oxide (DMPO) was used as a free radical scavenger to capture superoxide radicals (·O₂). 2- ) and hydroxyl radicals (·OH), such as Figure 8 As shown, no DMPO-·OH or DMPO-·O were observed in the dark. 2- The signal, after 5 minutes of illumination, showed that Example 1 CoP3 / CdZnS exhibited obvious DMPO-·O 2- The signal also showed a clear DMPO-·OH signal. However, Comparative Example 1, CdIn2S4, only captured a clear DMPO-·OH signal, while Comparative Example 2, CoP3, obtained a DMPO-·O signal. 2- The signal further confirms that the CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material has a Z-mechanism photocatalytic mechanism.

[0056] Figure 9The figures show the photocatalytic hydrogen production performance of the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared using the method described in Example 1 of this invention, and the photocatalytic materials of Comparative Examples 1 and 2. As can be seen from the figures, due to the rapid recombination of photogenerated electrons in Comparative Example 1 CoP3, the amount of H2 generated is almost negligible. The hydrogen production rate of Comparative Example 1 CdZnS is 2.11 mmol g⁻¹ h⁻¹, while the hydrogen production rate of the CoP3 / CdZnS photocatalytic material obtained in Example 1 is as high as 87.41 mmol g⁻¹. -1 h -1 It is 41 times that of the control group CdZnS.

[0057] Figure 10 The results show the cycle stability test of the Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material prepared using the method described in Example 1 of this invention. It can be seen that after 30 hours and 5 cycles of hydrogen production performance testing, the hydrogen production amount did not change significantly, indicating that the photocatalytic material prepared by the method described in this embodiment of the invention has excellent photocatalytic stability.

[0058] The composite photocatalytic material prepared by the method described in the embodiments of the present invention has excellent photocatalytic degradation performance when used for photocatalytic oxidation degradation of H2S, drugs and organic dyes in aqueous solution, and can be used for photocatalytic oxidation treatment of organic wastewater.

[0059] The composite photocatalytic material prepared by the method described in the embodiments of the present invention is used for the photocatalytic removal of harmful gases such as formaldehyde, nitrogen oxides and H2S in the air, and also has a good photocatalytic oxidation efficiency.

[0060] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, substitutions, simplifications, etc. made without departing from the principle and process of the present invention are equivalent substitutions and should be included within the protection scope of the present invention.

Claims

1. A Z-mechanism CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material, characterized in that, The pn heterojunction is composed of n-type CdZnS nanobuilding units modified with p-type CoP3 quantum dots, forming a CoP3 / CdZnS pn heterojunction. The CdZnS nanobuilding units possess dislocation defect structures, and the CoP3 quantum dot modification on the surface of the CdZnS nanobuilding units can form numerous tiny heterojunction interfaces. The CoP3 / CdZnS pn heterojunction nanobuilding units self-assemble into a sycamore-fruit-like self-assembled body. The photocatalytic material exhibits a Z-mechanism photocatalytic mechanism with high hydrogen production rate. It is used for the photocatalytic oxidation degradation of H2S, pharmaceuticals, and organic dyes in aqueous solutions, and for the photocatalytic removal of harmful gases such as formaldehyde, nitrogen oxides, and H2S from the air. Its preparation method specifically includes the following steps: (1) Dissolve 1-10 mmol Cd(NO3)2·4H2O, 1-10 mmol Zn(NO3)2·6H2O, and 1-50 mmol thiourea in 10-200 ml water and 10-200 ml ethylenediamine, stir for 30 min, transfer to a 50-500 ml autoclave, place in an oven at 100-220 °C for 3-24 h, remove, cool naturally to room temperature, centrifuge and dry to obtain a light yellow sycamore fruit-shaped CdZnS sample with dislocation defects; (2) Weigh 0.1-5.0 g of CdZnS sample obtained in step (1) and disperse it in water. Add 0.1-2.0 g of NaH2PO2, 0.01-2.0 g of CoCl2·6H2O, and 0.1-2.0 g of NaBH4 and dissolve them in 35-400 mL of deionized water. Stir for 30 min, transfer to a 50-500 mL stainless steel autoclave lined with polytetrafluoroethylene, and react at 100-220 °C for 3-24 h. Allow it to cool naturally to room temperature, centrifuge and dry to obtain CoP3 / CdZnS sycamore fruit-like pn heterojunction photocatalytic material.

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