Use of ternary s-type heterojunction photocatalyst

Abstract

The application of a ternary S-type heterojunction photocatalyst relates to the technical field of photocatalytic wastewater treatment, and solves the problems of insufficient synergistic response ability of different wavelengths of light, low spectral utilization rate, low energy utilization rate caused by the fact that the catalyst absorption peak cannot be effectively matched with the wide-spectrum light source, and the fact that the development of laser-coupled photocatalytic materials is not mature. The g-C3N4 powder is obtained by calcining urea as a precursor; ZnO / Cu 1.35 O and g-C3N4 are mixed and heat-treated to obtain a ZnO / Cu 1.35 O / g-C3N4 composite photocatalyst, which can be applied to the field of photocatalytic degradation of organic pollutants. The application utilizes laser to match the characteristic absorption peak of the composite photocatalyst, realizes the synergistic response across the blue light and red light double bands, and significantly improves the spectral utilization efficiency, energy utilization rate, pollutant adsorption rate and degradation rate of the catalyst.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photocatalytic wastewater treatment, and particularly relates to application of a ternary S-type heterojunction photocatalyst in wastewater treatment. BACKGROUND

[0002] With the rapid development of industrialization and agricultural modernization, a large amount of industrial wastewater and agricultural non-point source pollution is continuously discharged into natural water bodies, causing continuous deterioration of water environmental quality and degradation of ecosystem function. In the face of complex and diverse types of pollutants and rising pollution load, traditional wastewater treatment technologies (such as physical sedimentation, chemical flocculation and biodegradation) are difficult to simultaneously consider treatment efficiency, economy and environmental friendliness. Photocatalytic technology is considered as a green treatment technology with great application prospect due to its advantages of utilizing sunlight, mild reaction conditions, no need for additional chemicals and complete mineralization of complex organic pollutants. Photocatalysts can generate electron-hole pairs after being excited by light, and these active carriers can participate in redox reactions to decompose organic pollutants in water bodies. However, traditional photocatalysts can only absorb specific narrow-band light and cannot achieve synergistic response to different wavelengths of ultraviolet light, visible light and infrared light, resulting in low spectral utilization rate. At the same time, existing photocatalytic systems mostly rely on ultraviolet lamps, halogen lamps or visible light lamps as wide-spectrum light sources, and their emission spectrum is continuous and wide, which is difficult to accurately match the characteristic absorption peak of the photocatalyst, and cannot provide efficient and directional light excitation for specific wavelengths, further causing spectral mismatch between energy input and photocatalytic demand, resulting in low light energy utilization efficiency and increasing actual operating energy consumption, low energy utilization rate, and restricting the economic feasibility of its large-scale application.

[0003] To overcome the above technical bottlenecks, researchers have tried to use zeolitic imidazolate frameworks (ZIFs) with unique pore structure and adjustable chemical properties as photocatalysts or photocatalyst carriers, which can effectively regulate light absorption, improve the separation efficiency of photo-generated electron-hole and photocatalytic stability, and promote the rapid diffusion of pollutants through their three-dimensional channels. However, its structural characteristics still cannot break through the bottleneck of limited spectral response range, and the light energy cannot be fully utilized, and its photocatalytic efficiency under wide-spectrum light source or sunlight conditions is still significantly limited.

[0004] In recent years, laser has the characteristics of high monochromaticity, large energy density, good directionality and precise control of light wavelength, and is expected to be applied in the field of photocatalysis. However, the development of laser-coupled photocatalytic materials is still in its initial stage, and the related research on composite material systems that can simultaneously achieve high matching of light absorption with specific wavelengths of laser, wide-spectrum response and efficient photo-generated charge separation is still immature.

[0005] Therefore, developing a new laser-coupled photocatalyst capable of widening the spectral response range, improving the spectral utilization and energy utilization, and realizing double-band light response has practical significance for breaking through the performance bottleneck of traditional photocatalytic systems and promoting the engineering and large-scale application of wastewater treatment technology. SUMMARY

[0006] In order to solve the problems of insufficient synergistic response ability of different wavelengths of light, low spectral utilization, low energy utilization due to the mismatch between the catalyst absorption peak and the wide spectrum light source, and immature development of laser-coupled photocatalytic materials, the application of a ternary S-type heterojunction photocatalyst is proposed. The technical scheme of the application is as follows:

[0007] The application of a ternary S-type heterojunction photocatalyst, the ternary S-type heterojunction photocatalyst cooperates with an excitation light source applied in the field of wastewater treatment;

[0008] The ternary S-type heterojunction photocatalyst is a ZnO / Cu 1.35 O / g-C3N4 composite photocatalyst;

[0009] The excitation light source is a red light band laser lamp, a blue light band laser lamp, or a red and blue mixed band laser lamp.

[0010] Further, it is applied in the field of photocatalytic degradation of organic pollutants.

[0011] Further, the preparation of the ternary S-type heterojunction photocatalyst includes the following steps:

[0012] S1: Mix and stir a zinc nitrate hexahydrate methanol solution and a dimethyl imidazole methanol solution, stand, centrifuge, collect the precipitate, dry, and obtain ZIF-8;

[0013] S2: Mix and stir the ZIF-8 powder with a copper ion solution, stand, centrifuge, collect the precipitate, dry, and obtain ZIF-8 / Cu; calcine the ZIF-8 / Cu powder to obtain ZnO / Cu 1.35 O;

[0014] S3: Calcine urea as a precursor, heat preservation, and obtain g-C3N4 powder;

[0015] S4: Mix ZnO / Cu 1.35 O and g-C3N4, add deionized water, ultrasonic, adjust pH, heat treat the mixed solution, discard the supernatant, centrifuge, wash, and obtain a ZnO / Cu 1.35 O / g-C3N4 composite photocatalyst.

[0016] Further, the rotating speed of the mixing and stirring in S1 is 300-500 r / min, the time of the mixing and stirring is 30-60 min; the time of the standing is 24-28 h; the rotating speed of the centrifugation is 9000-11000 r / min, the time of the centrifugation is 8-10 min; the drying temperature is 50-70 DEG C; the drying time is 24-36 h; the concentration of the zinc nitrate hexahydrate methanol solution is 0.06 g / mL; the concentration of the dimethyl imidazole methanol solution is 0.13 g / mL.

[0017] Further, the copper ion solution in S2 is any one of anhydrous copper sulfate solution, copper nitrate solution or copper chloride solution; the stirring time is 5 h, the rotating speed of the stirring is 400-600 r / min; the standing time is 18-28 h; the rotating speed of the centrifugation is 9000-12000 r / min, the time of the centrifugation is 8-10 min; the drying temperature is 50-70 DEG C; the drying time is 24-36 h.

[0018] Further, the calcination in S2 is heated to 550 DEG C at a heating rate of 2 DEG C / min under the protection of nitrogen atmosphere, and kept for 30 min; the molar ratio of the ZIF-8 to copper ions in the copper ion solution is 1.25:1.

[0019] Further, the calcination in S3 is heated to 550 DEG C at a heating rate of 2 DEG C / min; the heat preservation is kept at 550 DEG C for 4 h.

[0020] Further, the mass ratio of the ZnO / Cu 1.35 O to g-C3N4 in S4 is 1-3:1-3; the ultrasonic power is 400 W, and the ultrasonic time is 30 min.

[0021] Further, the pH adjustment is adjusted to 8.9-9.1 by using NaOH aqueous solution; the heat treatment is heated to 160 DEG C at a heating rate of 2 DEG C / min and kept for 12 h, and naturally cooled to 30 DEG C.

[0022] Further, the rotating speed of the centrifugation in S4 is 10000 r / min, and the centrifugation time is 10 min; the washing is sequentially washed 3 times by using hydrochloric acid, anhydrous ethanol and deionized water.

[0023] Compared with the prior art, the application solves the problems of insufficient synergistic response ability of different wavelengths of light, low spectral utilization rate, dependence on wide spectrum light source leading to ineffective matching with catalyst absorption peak, low energy utilization rate, and immature development of laser coupled photocatalytic materials, and has the following specific beneficial effects:

[0024] 1.The application realizes the high matching of different energy band structures and interface built-in electric field by regulating the mass ratio of ZnO / Cu 1.35 O and g-C3N4, and constructs the composite synergistic system of ZnO / Cu 1.35 O / g-C3N4 ternary S-type heterojunction and II-type heterojunction. In the system, the characteristics of g-C3N4 absorbing blue light band and Cu 1.35 O absorbing red light band and the function of ZnO as an electron acceptor are utilized to realize the synergistic response across the double bands of blue light and red light. Cu 1.35 O rich in copper vacancies can provide efficient electron trapping and transfer channels due to its wide absorption range extending to near-infrared and unique defect energy level, and can form a significant potential barrier effect after being combined with the heterojunction interface, so that the photo-generated electrons and holes can be quickly separated and directionally migrated in space, and the bulk and interface recombination can be effectively inhibited. At the same time, the surface amino and pi conjugated structure of g-C3N4 provide adsorption active sites, which can realize the rapid enrichment of pollutants, so that the photo-generated electrons / holes and free radicals can directly act on the high local concentration of pollutants, significantly improving the photo-generated charge separation efficiency and pollutant adsorption efficiency of the photocatalytic material under blue light and red light.

[0025] 2.The application precisely matches the characteristic absorption peaks of ZnO / Cu 1.35 O / g-C3N4 composite photocatalyst by laser, so that the high-energy photons and low-energy photons are precisely matched with the energy level transitions of g-C3N4 and Cu 1.35 O, respectively, to realize the cross-spectrum synergistic response under laser driving, effectively improving the spectral utilization efficiency, the generation rate of photo-generated carriers, and the pollutant degradation rate compared with visible light and ultraviolet light. Under blue light band laser irradiation, the photo-generated electrons generated by the excitation of g-C3N4 migrate to ZnO, and the photo-generated electrons generated by the excitation of Cu 1.35 O also transfer to ZnO, so that the excitation energy of two semiconductors in the same band is converted into available electrons; while under red light band laser irradiation, Cu 1.35 O absorbs low-energy photons and transfers electrons to g-C3N4, and ZnO continuously receives electrons from g-C3N4 as an electron sink, so that the charge flow directions are spatially separated under the double bands. In addition, the laser can continuously and high-energy density excite the photocatalyst, effectively overcoming the disadvantages of random, dispersion and large energy density fluctuation of sunlight, and fundamentally improving the generation rate of photo-generated charges and the participation efficiency of effective carriers.

[0026] 3. The present application utilizes the synergistic effect of low-power laser lamp-catalyst after adsorption enrichment and in-situ degradation, which fundamentally reduces the dependence on light intensity, effectively improves the energy utilization rate, and reduces energy consumption; at the same time, the amount of surfactant and organic solvent on the surface of the catalyst is reduced during preparation, the reaction utilization rate is improved, and the requirements of green chemical industry and sustainable material preparation are met. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is the quasi-first-order adsorption kinetics curve of ZnO / Cu 1.35 O / g-C3N4 composite photocatalyst;

[0028] Figure 2 is the quasi-second-order adsorption kinetics curve of ZnO / Cu 1.35 O / g-C3N4 composite photocatalyst;

[0029] Figure 3 is the photocatalytic degradation curve of ZCG-1;

[0030] Figure 4 is the photocatalytic degradation curve of ZCG-2;

[0031] Figure 5 is the scanning electron microscope image of ZCG-2;

[0032] Figure 6 is the nitrogen adsorption-desorption isotherm curve of ZCG-2;

[0033] Figure 7 is the pore size distribution curve of ZCG-2;

[0034] Figure 8 is the photocatalytic degradation curve of ZCG-3;

[0035] Figure 9 is the infrared spectrum of ZCG-1~3;

[0036] Figure 10 is the X-ray diffraction spectrum of ZCG-1~3;

[0037] Figure 11 is the photoluminescence spectrum of ZCG-1~3;

[0038] Figure 12 is the X-ray photoelectron spectroscopy of ZCG-1~3. DETAILED DESCRIPTION

[0039] In order to make the technical solutions of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings of the specification of the present application. It should be noted that the following embodiments are only used to better understand the technical solutions of the present application, and should not be understood as a limitation of the present application.

[0040] Embodiment 1.

[0041] S1: 6 g of zinc nitrate hexahydrate was dissolved in 100 mL of methanol, 13 g of dimethylimidazole was dissolved in 100 mL of methanol, the zinc nitrate hexahydrate methanol solution was poured into the dimethylimidazole methanol solution, stirred at a speed of 500 r / min for 30 min, and after standing for 24 h, a centrifuge with a speed of 10000 r / min was used to centrifuge for 10 min, and the precipitate was collected; then the collected precipitate was placed in an oven at 60℃ for drying for 24 h, to obtain ZIF-8;

[0042] S2: The ZIF-8 was ground into powder, 2 g of ZIF-8 powder was weighed and mixed with 450 mL of anhydrous copper sulfate solution according to a molar ratio of 1.25:1, stirred at a speed of 500 r / min for 5 h, and after standing for 24 h, a centrifuge with a speed of 10000 r / min was used to centrifuge for 10 min, and the precipitate was collected; then the collected precipitate was placed in an oven at 60℃ for drying for 24 h, to obtain ZIF-8 / Cu; the ZIF-8 / Cu powder was placed in a tube furnace, heated to 550℃ at a heating rate of 2 ℃ / min under the protection of nitrogen atmosphere, and calcined at this temperature for 30 min, to obtain ZnO / Cu 1.35 O;

[0043] S3: Urea was used as a precursor, heated to 550℃ at a heating rate of 2 ℃ / min in a muffle furnace, and kept for 4 h, to obtain g-C3N4 powder;

[0044] S4: 0.75 g of ZnO / Cu 1.35 O powder was dispersed in 50 mL of deionized water, 0.25 g of g-C3N4 powder was dispersed in 10 mL of deionized water; the two suspensions were mixed and ultrasonically treated for 30 min under a power of 400 W to ensure that they were fully uniform. After adjusting the pH of the mixed solution to 9.0±0.1 with a NaOH aqueous solution, the mixed solution was transferred to a polytetrafluoroethylene liner with a filling degree of less than 80%, heated to 160℃ at a heating rate of 2 ℃ / min and kept for 12 h; after natural cooling to below 30℃, the supernatant was discarded, centrifuged at a speed of 10000 r / min for 10 min, and then washed with 0.01M hydrochloric acid, anhydrous ethanol and deionized water for 3 times in turn, to prepare ZnO / Cu 1.35The O / g-C3N4 composite photocatalyst is designated as ZCG-1.

[0045] Example 2.

[0046] The difference between this embodiment and Embodiment 1 is that 0.5 g of ZnO / Cu is used in S4. 1.35 A dispersion was prepared by reacting O with 0.5 g of g-C3N4, and the remaining preparation steps and conditions were the same as in Example 1, yielding ZnO / Cu 1.35 The O / g-C3N4 composite photocatalyst is designated as ZCG-2.

[0047] Example 3.

[0048] The difference between this embodiment and Embodiment 1 is that 0.25 g of ZnO / Cu is used in S4. 1.35 A dispersion was prepared using O and 0.75 g g-C3N4; the remaining preparation steps and conditions were the same as in Example 1, yielding ZnO / Cu 1.35 The O / g-C3N4 composite photocatalyst is designated as ZCG-3.

[0049] Pollutant adsorption experiment:

[0050] Using tetracycline hydrochloride (TCH) as a simulated pollutant, ZnO / Cu was subjected to treatment in the dark. 1.35 Adsorption experiment of tetracycline hydrochloride on O / g-C3N4 composite photocatalyst. 15 mg of the ZCG-1~3 composite photocatalyst prepared in Examples 1-3 was taken and added to quartz tubes containing 30 mL of 30 mg / L TCH. The suspension was magnetically stirred in the dark for 20 min, and 3 mL of solution was taken from each tube using a 0.45 μm filter membrane to measure the absorbance value.

[0051] like Figure 1 , Figure 2 ZnO / Cu prepared in Examples 1-3 respectively 1.35The quasi-first-order adsorption kinetic curves and quasi-second-order adsorption kinetic curves of the O / g-C3N4 composite photocatalyst can be seen from the comparison of the two figures. The three composite photocatalysts ZCG-1 to ZCG-3 all exhibit a rapid initial adsorption characteristic in the dark condition, and the adsorption amount increases sharply in the early stage, and then gradually tends to be stable and approaches the respective equilibrium adsorption capacity. Under the quasi-first-order kinetic model, the adsorption curves of ZCG-1 and ZCG-2 both exhibit a typical exponential decline characteristic, indicating that the adsorption rate is mainly controlled by the number of unoccupied sites on the surface, and the fitting curves of the two are in good agreement with the experimental data, indicating that the quasi-first-order model can reasonably describe the adsorption process; although the adsorption trend of ZCG-3 also exhibits a rapid-moderate stage change, the overall fitting degree is slightly lower than that of the former two, and its adsorption behavior may also include other kinetic contributions. Under the quasi-second-order kinetic model, the curves of ZCG-1 and ZCG-2 further exhibit a higher fitting correlation, and the equilibrium adsorption capacity is close to the experimental value, indicating that the adsorption process has more obvious characteristics in terms of electron exchange or interface chemical action; ZCG-3 also exhibits an observable fitting trend under this model, but its equilibrium adsorption capacity is significantly lower than that of the former two, indicating that the number of effective sites available for binding on its surface is less, and the interface binding capacity is also relatively limited.

[0052] Comprehensive analysis Figure 1 and Figure 2 It can be seen that the ZnO / Cu 1.35 The O / g-C3N4 composite photocatalyst exhibits a typical rapid adsorption behavior for tetracycline hydrochloride (TCH), and gradually reaches a stable interval in a short time. It is proved that the surface of the photocatalyst provided by the application has a large number of active sites available for TCH molecules to bind, which is due to the surface amino group and π conjugated structure of g-C3N4 providing adsorption active sites, which can realize the rapid enrichment of pollutants, so that the photo-generated electrons / holes and free radicals can directly act on the high local concentration of pollutants; at the same time, the photocatalyst has good interface affinity, so that the TCH in the solution can be quickly enriched on the surface of the photocatalyst in the dark environment, forming an obvious adsorption layer. With the passage of time, the curve gradually stabilizes and maintains a stable adsorption capacity, proving that the adsorption capacity of the photocatalyst provided by the application is stable and reliable, and the structure integrity and interface binding durability are maintained after reaching equilibrium. In addition, the application constructs an S-type heterojunction structure between ZnO, Cu 1.35 O and g-C3N4, so that a built-in electric field and a steady-state electron distribution are formed at the interface, thereby enhancing the polar sites, electron enrichment area and interface interaction strength on the surface of the catalyst, making it easier for the phenolic hydroxyl group, amide group and other functional groups in the TCH molecule to bind to the material surface, providing an effective pollutant enrichment basis for subsequent photocatalytic degradation of the composite photocatalyst in the dark.

[0053] Photocatalytic degradation experiment:

[0054] Take 15 mg of the ZCG-1~3 composite photocatalyst prepared in Examples 1-3, and add them to quartz tubes containing 30 mL of 30 mg / L TCH. Stir the suspension magnetically in the dark for 20 min to reach adsorption-desorption equilibrium. Then, irradiate the solution with a mercury lamp (360 W), a red laser lamp (13 W), a blue laser lamp (13 W), and a mixed red-blue laser lamp (13 W RB). Take 3 mL of solution and sample every 20 min. Measure the remaining TCH content in the filtrate using a UV-Vis spectrophotometer (UV-2250) at a wavelength of 357 nm. The degradation rate (DR) can be calculated using the following formula:

[0055] DR (%) = C t / C0×100%;

[0056] Where C0 is the initial concentration after the dark reaction, C t The concentration of the sample after degradation.

[0057] like Figure 3 The figure shows the photocatalytic degradation curve of ZCG-1. As can be seen from the figure, the catalyst exhibits the highest degradation rate under RB light excitation, with the curve showing a rapid and continuous decrease. This demonstrates that the photogenerated carrier channels in the ternary S-type heterojunction of the ZCG-1 structure are most fully activated in the red-blue mixed wavelength band, utilizing the absorption of blue light by g-C3N4 and Cu... 1.35 The absorption of red light by oxygen and the electron acceptor function of ZnO enable a synergistic response across both blue and red light bands. Under blue light laser irradiation, photogenerated electrons generated by the excitation of g-C3N4 migrate to ZnO, while Cu... 1.35 The photogenerated electrons generated by the excitation of O are also transferred to ZnO, so that the excitation energy of both semiconductors in the same wavelength band is converted into usable electrons; while under red light laser irradiation, Cu 1.35 O absorbs low-energy photons and transfers electrons to g-C3N4, while ZnO continuously acts as an electron sink, receiving electrons from g-C3N4. This results in spatially separated charge flow directions in both wavelength bands, effectively improving the degradation rate. W light (mercury lamp), due to its broad spectrum including the ultraviolet region, showed a lower initial degradation rate than RB light in this system. This indicates that ZCG-1 has a higher spectral matching degree in the visible light region, while the dual-band RB light better matches the absorption window of the ternary heterojunction. The slower initial degradation rate of the UV group is due to the fact that the transition near 357 nm is mainly dominated by ZnO, leading to a decrease in Cu in the photocatalyst. 1.35The participation of O and g-C3N4 is limited, and thus the degradation rate in the early stage is slower. The overall degradation rate of B light is lower than that of other light conditions due to the narrow excitation range, which shows the limitations of single-band excitation in ternary systems.

[0058] As shown in Figure 4 The photocatalytic degradation curve of ZCG-2 is shown, and the overall curve trend is consistent with ZCG-1. As can be seen from the figure, the synergistic excitation of RB light still maintains the best catalytic effect, which is due to the fact that ZnO / Cu 1.35 When O and g-C3N4 are in a mass ratio of 1:1, the electron and hole migration paths tend to be balanced, and the advantages of S-type heterojunction are more obvious. Cu 1.35 The coupling degree between O and g-C3N4 is enhanced, so that the double-band of RB can almost simultaneously excite the key absorption peak of both, thus the degradation rate is significantly improved. The degradation rate of W light is significantly lower than that of ZCG-1, which is due to the fact that the content of ZnO in ZCG-2 is reduced, resulting in a decrease in the absorption ability of UV light. The absorption window of UV light in the ternary photocatalytic material is not matched, which makes the contribution of photo-generated carriers insufficient. In addition, although R light and B light can both drive photocatalytic reactions, due to the difficulty of single narrow-spectrum excitation in establishing a complete electron transport chain in the ternary system, their degradation effects are lower than that of RB light. 1.35

[0059] The scanning electron microscope (SEM) test of ZCG-2 prepared in Example 2 is shown in Figure 5 As can be seen from the figure, ZCG-2 has a stacked and close-grained or sheet-like structure, a rough surface and small pores, which indicates that the multiphase composite process of the photocatalyst forms a high specific surface area and a continuous electron or substance transport channel, providing more active sites for adsorption and photocatalytic reaction.

[0060] Figure 6 The isotherm curve of nitrogen adsorption-desorption of ZCG-2 is shown, which presents a typical type IV characteristic with obvious hysteresis loop, indicating that ZCG-2 is mainly mesoporous, with regular pore structure and good connectivity, which is beneficial to the diffusion and transmission of molecules inside.

[0061] The pore size distribution curve of ZCG-2 is shown in Figure 7 As can be seen from the figure, the pore size of ZCG-2 is mainly concentrated in the range of 0~20 nm, and the distribution is uniform. This mesopore size can effectively accommodate target pollutant molecules into the pore channel, increase the actual specific surface area, and at the same time, help to reduce the diffusion resistance, making the mass transfer process of reactants and products in the pore channel more smooth.

[0062] ​As Figure 8 The photocatalytic degradation curves of ZCG-3 are shown in the figure, and it can be seen from the figure that the degradation rates all show a rapid downward trend within 20 min before the reaction, which indicates that under the condition of a large increase in the content of g-C3N4, the strong absorption of visible light by itself and the enrichment effect of the surface active site make the synergistic effect of initial adsorption and photoexcitation significantly enhanced. However, as the reaction enters 20-90 min, the curves gradually tend to be flat, which indicates that in a high proportion of g-C3N4, the carrier migration path may have a tendency to excessively concentrate in a single phase, so that the built-in electric field in the S-shaped heterojunction interface is weakened compared with ZCG-1 and ZCG-2. The recognition rate of R light is the slowest in the early stage, which reflects that R light excitation mainly acts on Cu 1.35 O, and in the case of a large proportion of g-C3N4, the starting point of electron transfer is limited, so the initial catalytic efficiency is low. However, as the reaction continues, a directional migration path can still be formed at the three-phase interface, so the final result is consistent with that of other light groups. The double-band excitation of RB light makes the π-π* transition of g-C3N4 and the visible light absorption of Cu 1.35 O are all responded at the same time, so that the interfacial charge transport channel is quickly established in the early stage, and a high separation efficiency is maintained throughout the reaction process, and the final degradation rate tends to 0.

[0063] The infrared spectra of ZCG-1-3 prepared in Example 1-3 are shown in the figure Figure 9 The infrared spectra of ZCG-1-3 are shown in the figure, and it can be seen from the figure that ZCG-1-3 all appear O-H or N-H stretching vibration peaks at 3400-3200 cm -1 , which indicates that there are hydroxyl or amine functional groups on the surface of the photocatalyst material; C=O or C=N stretching peaks appear at about 1630 cm -1 , and C–N or C–O stretching vibration peaks appear in the range of 1400-1200 cm -1 , which indicates that the multi-phase components in the photocatalyst provided by the present application have been effectively combined to form a composite interface; the fingerprint region absorption peaks in the range of 500-1000 cm -1 correspond to the skeleton characteristic peaks of Zn–O or Cu–O, which reflects the existence and stability of the metal oxide skeleton. It is proved that the photocatalyst provided by the present application successfully realizes the composite of multi-component materials, and the multi-phase interface structure is clear, which provides a basis for its excellent adsorption and photocatalytic performance.

[0064] The X-ray diffraction spectra of ZCG-1-3 prepared in Example 1-3 are shown in the figure Figure 10 , and it can be seen from the figure that g-C3N4 (2θ≈27.5°), ZIF-8 (2θ≈7.3°, 10.4°), ZnO / Cu 1.35The characteristic peaks of O (2θ ≈ 36.3°) are basically consistent with those of a single phase, which proves that the photocatalyst provided by the application successfully integrates multiple components, and the crystal structures of the components are not obviously damaged in the compounding process, and still maintain the respective crystal phase characteristics.

[0065] Figure 11 The photoluminescence spectra of ZCG-1-3 prepared in Examples 1-3 are shown in the figure, from which it can be seen that the luminescence peaks of the ZCG-1-3 photocatalysts are concentrated near 500 nm, wherein the luminescence intensity of ZCG-1 is relatively higher, while the luminescence intensity of ZCG-2 and ZCG-3 is slightly lower and the peak shape is closer; the luminescence peak positions of the three are not obviously shifted, which indicates that the luminescence center structures of the three materials are basically consistent.

[0066] Figure 12 The X-ray photoelectron spectrograms of ZCG-1-3 prepared in Examples 1-3 are shown in the figure, from which it can be seen that the spectrograms of ZCG-1-3 all detect the characteristic binding energy peaks of Zn 2p, Cu 2p, O 1s, N 1s and C 1s, which proves that the multiple components are successfully introduced into the catalyst material and the chemical composition is stable, which ensures the integrity of the material composition and effectively realizes the regulation of the electronic structure.

[0067] In summary, the ZnO / Cu 1.35 O and g-C3N4, and then realizes the high matching of different energy band structures and interface built-in electric fields, and constructs the compounding and synergistic system of the ZnO / Cu 1.35 O / g-C3N4 ternary S-type heterojunction and II-type heterojunction, realizes the synergistic response across the blue light and red light double bands, and significantly improves the photo-generated charge separation efficiency and pollutant adsorption efficiency of the photocatalytic material under the blue light band and the red light band. 1.35 The characteristic absorption peaks of the ZnO / Cu 1.35 O / g-C3N4 composite photocatalyst, so that the high-energy photons and low-energy photons are accurately matched with the energy level transitions of g-C3N4 and Cu 1.35 O, respectively, realizes the cross-spectrum synergistic response under the laser driving, and the laser can continuously and high-energy density excite the photocatalyst, effectively improves the spectral utilization efficiency, the generation rate of photo-generated carriers and the pollutant degradation rate.

[0068] The above examples are only used to help understand the method of the application and its core idea. It should be noted that for those skilled in the art, without departing from the principles of the application, some improvements and modifications can be made to the application, and these improvements and modifications also fall within the protection scope of the claims of the application.

[0069] The foregoing description of the embodiments disclosed enables a person skilled in the art to make or use the application. Numerous modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without the use of the inventive faculty. Therefore, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A ternary S-type heterojunction photocatalyst, characterized by, Ternary s-type heterojunction photocatalyst is ZnO / Cu 1.35 O / g-c3n4 composite photocatalyst The preparation of the ternary S-type heterojunction photocatalyst comprises the following steps: S1: mixing and stirring a zinc nitrate hexahydrate methanol solution and a dimethyl imidazole methanol solution, standing, centrifuging, collecting the precipitate, drying, and obtaining ZIF-8; S2: mixing ZIF-8 powder with copper ion solution, stirring, standing, centrifuging, collecting precipitate, drying to obtain ZIF-8 / Cu; calcining ZIF-8 / Cu powder to obtain ZnO / Cu 1.35 O; S3: calcining urea as a precursor, and keeping warm to obtain g-C3N4 powder; S4: ZnO / Cu 1.35 O / g-C3N4 composite photocatalyst is prepared by mixing ZnO / Cu 1.35 O / g-C3N4 composite photocatalyst. 2.The ternary S-type heterojunction photocatalyst according to claim 1, characterized in that, The rotating speed of the mixing and stirring in S1 is 300-500 r / min, and the mixing and stirring time is 30-60 min; the standing time is 24-28 h; the rotating speed of the centrifuging is 9000-11000 r / min, and the centrifuging time is 8-10 min; the drying temperature is 50-70℃; the drying time is 24-36 h; the concentration of the zinc nitrate hexahydrate methanol solution is 0.06 g / mL; and the concentration of the dimethyl imidazole methanol solution is 0.13 g / mL. 3.The ternary S-type heterojunction photocatalyst according to claim 1, characterized in that, The copper ion solution in S2 is any one of anhydrous copper sulfate solution, copper nitrate solution or copper chloride solution; the stirring time is 5 h, and the rotating speed of the stirring is 400-600 r / min; the standing time is 18-28 h; the rotating speed of the centrifuging is 9000-12000 r / min, and the centrifuging time is 8-10 min; the drying temperature is 50-70℃; and the drying time is 24-36 h. 4.The ternary S-type heterojunction photocatalyst according to claim 1, characterized in that, The calcining in S2 is heating to 550℃ at a heating rate of 2℃ / min under nitrogen atmosphere protection, and keeping for 30 min; and the molar ratio of the ZIF-8 to copper ions in the copper ion solution is 1.25:

1. 5.The ternary S-type heterojunction photocatalyst according to claim 1, characterized in that, The calcining in S3 is heating to 550℃ at a heating rate of 2℃ / min; and the keeping warm is keeping at 550℃ for 4 h. 6.The ternary S-type heterojunction photocatalyst according to claim 1, characterized in that, ZnO / Cu 1.35 O and g-C3N4 is 1-3:1-3; the power of the ultrasonic is 400 W, and the ultrasonic time is 30 min. 7.The ternary S-type heterojunction photocatalyst according to claim 1, characterized in that, The pH adjustment is adjusting the pH to 8.9-9.1 with a NaOH aqueous solution; and the heat treatment is heating to 160℃ at a heating rate of 2℃ / min and keeping for 12 h, and naturally cooling to 30℃. 8.The ternary S-type heterojunction photocatalyst according to claim 1, characterized in that, The rotating speed of the centrifuging in S4 is 10000 r / min, and the centrifuging time is 10 min; and the washing is washing with hydrochloric acid, anhydrous ethanol and deionized water in sequence for 3 times.

9. Use of the ternary S-type heterojunction photocatalyst according to any one of claims 1 to 8, characterized in that, The ternary S-type heterojunction photocatalyst cooperates with an excitation light source and is applied to the field of wastewater treatment. The excitation light source is a red light band laser lamp, a blue light band laser lamp or a red and blue mixed band laser lamp.

10. The use of the ternary S-type heterojunction photocatalyst according to claim 9, characterized by, It is applied to the field of photocatalytic degradation of organic pollutants.

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