ZnO / KPHI composite photocatalyst and preparation method and application thereof

Abstract

This invention relates to a method for preparing a ZnO / KPHI composite photocatalyst in the field of photocatalytic materials, comprising the following steps: S1, dissolving melamine and potassium chloride in deionized water at a mass ratio of 1:3-4, mixing at 85-95°C and holding at that temperature for 20-40 min, evaporating the water to obtain a solid mixture; grinding the solid mixture and heating it to 580-620°C at a heating rate of 4-6°C / min, calcining at that temperature for 1.5-2.5 h, and after natural cooling, washing, drying, and grinding to obtain a KPHI substrate; S2, using anhydrous chlorine... Zinc oxide and KPHI-based powders were added to deionized water and ultrasonically dispersed for 20-40 minutes. Sodium hydroxide solution was then added dropwise while stirring, controlling the molar ratio of NaOH to ZnCl2 to be 4.8-5.2:1. After the sodium hydroxide solution was completely added, stirring continued for 20-40 minutes to obtain the reaction solution. The reaction solution was then sealed and reacted at 75-85℃ for 22-26 hours. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, washed, dried, and then ground to obtain a ZnO / KPHI composite photocatalyst with an S-shaped heterojunction. This method solves the problem of poor stability in current photocatalysts.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic materials, specifically to a ZnO / KPHI composite photocatalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen peroxide (H2O2) is a green oxidant whose decomposition products are only water and oxygen. It is widely used in many fields such as industrial bleaching, fine chemical synthesis, medical disinfection, and industrial wastewater treatment. Currently, more than 90% of the world's hydrogen peroxide is produced by the traditional anthraquinone process. This process has problems such as a lengthy process flow, high energy consumption, and the need for large amounts of toxic organic solvents. At the same time, high-concentration industrial hydrogen peroxide is prone to decomposition and explosion during long-distance transportation and storage, posing a great safety hazard.

[0003] Photocatalytic in-situ synthesis of hydrogen peroxide utilizes sunlight to drive the reaction of water and oxygen to produce H2O2 under ambient temperature and pressure, representing a highly promising green distributed synthesis technology. Existing commonly used photocatalytic materials such as graphitic carbon nitride, pure KPHI, and pure ZnO all suffer from significant instability. For example, graphitic carbon nitride has low crystallinity and numerous lattice defects, leading to rapid recombination of photogenerated electron-hole pairs; pure ZnO has high electron mobility but weak visible light response and is prone to photocorrosion; pure KPHI's band structure is well-suited for hydrogen peroxide production, but its high recombination efficiency of photogenerated carriers means that even under high light intensity, the number of effective electrons participating in the reaction is extremely small, resulting in problems such as low yield, easy deactivation, and high cost.

[0004] Combining different semiconductor materials to prepare heterojunctions is a common method to improve photocatalytic performance. However, traditional type II heterojunctions lead to a decrease in the thermodynamic driving force of oxygen reduction in the system. At present, the field of photocatalytic hydrogen peroxide production generally faces technical bottlenecks such as high recombination rate of photogenerated carriers, poor oxygen reduction selectivity, low visible light utilization, small catalyst specific surface area, and insufficient catalytic efficiency and stability. Improving charge separation efficiency can suppress the rapid recombination of photogenerated electrons and holes, improve visible light utilization, and alleviate catalyst photocorrosion deactivation. Improving reactant adsorption capacity can improve oxygen reduction selectivity and fully utilize the photogenerated electron reaction efficiency. The synergy of these two approaches is expected to overcome the above-mentioned technical bottlenecks simultaneously. However, how to improve charge separation efficiency and reactant adsorption capacity while retaining the strong redox energy level of the material is currently a mature technical problem that has not yet been reported and remains an urgent issue to be solved in this field. Summary of the Invention

[0005] The present invention aims to provide a ZnO / KPHI composite photocatalyst, its preparation method and application, in order to solve the problem of poor stability of current photocatalysts.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a ZnO / KPHI composite photocatalyst, comprising the following steps: S1, melamine and potassium chloride are dissolved in deionized water at a mass ratio of 1:3~4, mixed at 85~95℃ and kept at the temperature for 20~40 min, and the water is evaporated to obtain a solid mixture; the solid mixture is ground and heated to 580~620℃ at a heating rate of 4~6℃ / min, calcined at the constant temperature for 1.5~2.5 h, and after natural cooling, washed, dried and ground, KPHI substrate is obtained; S2, add anhydrous zinc chloride and KPHI base powder to deionized water, ultrasonically disperse for 20-40 min, add sodium hydroxide solution dropwise while stirring, control the molar ratio of NaOH to ZnCl2 to be 4.8-5.2:1, and continue stirring for 20-40 min after the sodium hydroxide solution is completely added to obtain the reaction solution; S3. The reaction solution was sealed and placed in an environment of 75~85℃ for 22~26h. After the reaction was completed, it was cooled to room temperature, centrifuged, washed, dried and ground to obtain a ZnO / KPHI composite photocatalyst with an S-shaped heterojunction.

[0007] Preferably, as an improvement, in step S2, the theoretical mass fraction of ZnO in the final composite photocatalyst is 1%~10% by adjusting the amount of KPHI added.

[0008] Preferably, as an improvement, in step S2, the theoretical mass fraction of ZnO in the final composite photocatalyst is 3% by adjusting the amount of KPHI added.

[0009] Preferably, as an improvement, in step S3, after sealing the reaction solution, it is transferred to a reaction vessel or a constant temperature drying oven, and the in-situ hydrolysis reaction is maintained at 80°C for 24 hours.

[0010] A ZnO / KPHI composite photocatalyst, wherein the ZnO / KPHI composite photocatalyst is an S-type heterojunction photocatalyst and has a porous mesoporous morphology.

[0011] Preferably, as an improvement, the ZnO / KPHI composite photocatalyst is prepared by the same method used for preparing ZnO / KPHI composite photocatalysts. A ZnO / KPHI composite photocatalyst is applied to the in-situ synthesis of hydrogen peroxide through oxygen two-electron reduction driven by visible light or the full spectrum.

[0012] The advantages of this solution are: 1. This invention utilizes work function to induce a spontaneous built-in electric field (IEF) and band bending at the KPHI-ZnO interface. Under full-spectrum / visible light illumination, electrons with weak reducing power in the ZnO conduction band and holes with weak oxidizing power in the KPHI valence band undergo precise nonradiative recombination and annihilation at the interface. This selectively retains and enriches electrons with extremely high reducing activity in the KPHI conduction band, with an energy potential of approximately -0.65V vs. NHE. This energy potential perfectly matches and significantly accelerates the two-electron oxygen reduction (O2) of adsorbed oxygen. - The intermediate path completely breaks the inherent limitations of the sacrificial reduction energy level in conventional type II heterojunctions.

[0013] 2. This scheme exhibits a unique interlayer "spreading effect" through the in-situ deposition process of trace amount (3%) ZnO. The originally tightly stacked bulk KPHI with small specific surface area and scarce exposed sites has a significant emergence of porous mesoporous structure after composite deposition, and the specific surface area has increased dramatically by nearly 9 times, which greatly enhances the dynamic adsorption-diffusion mass transfer kinetics of dissolved oxygen (O2) and reactive protons.

[0014] 3. In the reaction system, the ZnO / KPHI prepared by this invention exhibits excellent photocatalytic H2O2 production performance, and its H2O2 accumulation is significantly better than that of pure KPHI and single ZnO; and it still maintains high activity after continuous cycle stability test. Attached Figure Description

[0015] Figure 1 These are field emission scanning electron microscope (FESEM) comparison images of pure KPHI (a), 3% ZnO / KPHI (b), and single ZnO (c) in the embodiments of the present invention.

[0016] Figure 2 X-ray diffraction (XRD) patterns of KPHI, ZnO, and KPHI composite samples with different ZnO loadings.

[0017] Figure 3 High-resolution XPS spectra of pure KPHI, pure ZnO, and 3% ZnO / KPHI composite samples under light-shielded / light-illuminated conditions, where (a) C 1s, (b) O 1s, (c) N 1s, (d) K 2p, and (e) Zn 2p.

[0018] Figure 4 Comparison curves showing the yield evolution over time of in-situ total synthesis of H2O2 driven by oxygen reduction under xenon lamp irradiation. Detailed Implementation

[0019] The following detailed description illustrates the specific implementation method: Example 1 A method for preparing a ZnO / KPHI composite photocatalyst includes the following steps: S1, weigh 3.000g of melamine and 10.000g of pure KCl molten salt, add them together to 30ml of deionized water, mix with magnetic stirring, and heat to 90℃, hold for 30min to homogenize the precursors. Then heat to 100℃ to completely evaporate the water, obtaining a solid mixture. Transfer the solid mixture to an agate grinding mortar for fine grinding, then place it in a covered ceramic crucible, put it in a box-type muffle furnace, heat to 600℃ at a heating rate of 5℃ / min, and calcine at that temperature for 2h. After the furnace has completely cooled to room temperature, remove it and wash it 5 times with deionized water and anhydrous ethanol by centrifugation to ensure that residual potassium chloride is removed. Dry it in a 60℃ vacuum drying oven, grind it, and collect the supercrystalline KPHI substrate.

[0020] S2, accurately weigh 0.0335g of anhydrous ZnCl2 solid and 0.6466g of KPHI substrate powder obtained in step S1, add them together to 10ml of deionized water, place in an ultrasonic cleaner and continuously ultrasonically disperse for 30min to allow protons and zinc ions to electrostatically adsorb between the KPHI layers, then transfer to a magnetic stirrer and maintain steady stirring for 30min; while maintaining high-speed stirring, slowly add 10mL of prepared NaOH solution dropwise to the above suspension through a microsyringe, adjusting the total molar ratio of NaOH to ZnCl2 to 5:1, and continue vigorous stirring for 30min after the addition is completed to obtain the reaction solution.

[0021] S3. Transfer the reaction solution from step S2 to a sealed reaction vessel and place it in a constant-temperature drying oven. Maintain a gentle, low-temperature reaction at 80°C for 24 hours. After the system has completely cooled to ambient temperature, collect the bottom precipitate by high-speed centrifugation. Wash and separate the precipitate four times with deionized water and anhydrous ethanol to thoroughly remove free Na. + and Cl - Ultimately, a 3% ZnO / KPHI composite photocatalyst with high specific surface area interfacial coupling was obtained.

[0022] Example 2 A method for preparing a ZnO / KPHI composite photocatalyst includes the following steps: S1, weigh 3.000g of melamine and 10.000g of pure KCl molten salt, add them together to 30ml of deionized water, mix with magnetic stirring, and heat to 90℃, hold for 30min to homogenize the precursors. Then heat to 100℃ to completely evaporate the water, obtaining a solid mixture. Transfer the solid mixture to an agate grinding mortar for fine grinding, then place it in a covered ceramic crucible, put it in a box-type muffle furnace, heat to 600℃ at a heating rate of 5℃ / min, and calcine at that temperature for 2h. After the furnace has completely cooled to room temperature, remove it and wash it 5 times with deionized water and anhydrous ethanol by centrifugation to ensure that residual potassium chloride is removed. Dry it in a 60℃ vacuum drying oven, grind it, and collect the supercrystalline KPHI substrate.

[0023] S2, accurately weigh 0.0335g of anhydrous ZnCl2 solid and 1.9800g of KPHI substrate powder prepared in step S1, add them together to 10ml of deionized water, place in an ultrasonic cleaner and continuously ultrasonically disperse for 30min to allow protons and zinc ions to electrostatically adsorb between the KPHI layers, then transfer to a magnetic stirrer and maintain steady stirring for 30min; while maintaining high-speed stirring, slowly add 10mL of prepared NaOH solution dropwise to the above suspension through a microsyringe, adjusting the total molar ratio of NaOH to ZnCl2 to 5:1, and continue vigorous stirring for 30min after the addition is completed to obtain the reaction solution.

[0024] S3. Transfer the reaction solution from step S2 to a sealed reaction vessel and place it in a constant-temperature drying oven. Maintain a gentle, low-temperature reaction at 80°C for 24 hours. After the system has completely cooled to ambient temperature, collect the bottom precipitate by high-speed centrifugation. Wash and separate the precipitate four times with deionized water and anhydrous ethanol to thoroughly remove free Na. + and Cl - Ultimately, a 1% ZnO / KPHI composite photocatalyst with high specific surface area interfacial coupling was obtained.

[0025] Example 3 A method for preparing a ZnO / KPHI composite photocatalyst includes the following steps: S1, weigh 3.000g of melamine and 10.000g of pure KCl molten salt, add them together to 30ml of deionized water, mix with magnetic stirring, and heat to 90℃, hold for 30min to homogenize the precursors. Then heat to 100℃ to completely evaporate the water, obtaining a solid mixture. Transfer the solid mixture to an agate grinding mortar for fine grinding, then place it in a covered ceramic crucible, put it in a box-type muffle furnace, heat to 600℃ at a heating rate of 5℃ / min, and calcine at that temperature for 2h. After the furnace has completely cooled to room temperature, remove it and wash it 5 times with deionized water and anhydrous ethanol by centrifugation to ensure that residual potassium chloride is removed. Dry it in a 60℃ vacuum drying oven, grind it, and collect the supercrystalline KPHI substrate.

[0026] S2, accurately weigh 0.0335g of anhydrous ZnCl2 solid and 0.3800g of KPHI substrate powder obtained in step S1, add them together to 10ml of deionized water, place in an ultrasonic cleaner and continuously ultrasonically disperse for 30min to allow protons and zinc ions to electrostatically adsorb between the KPHI layers, then transfer to a magnetic stirrer and maintain steady stirring for 30min; while maintaining high-speed stirring, slowly add 10mL of prepared NaOH solution dropwise to the above suspension through a microsyringe, adjusting the total molar ratio of NaOH to ZnCl2 to 5:1, and continue vigorous stirring for 30min after the addition is completed to obtain the reaction solution.

[0027] S3. Transfer the reaction solution from step S2 to a sealed reaction vessel and place it in a constant-temperature drying oven. Maintain a gentle, low-temperature reaction at 80°C for 24 hours. After the system has completely cooled to ambient temperature, collect the bottom precipitate by high-speed centrifugation. Wash and separate the precipitate four times with deionized water and anhydrous ethanol to thoroughly remove free Na. + and Cl - Ultimately, a 5% ZnO / KPHI composite photocatalyst with high specific surface area interfacial coupling was obtained.

[0028] Example 4 A method for preparing a ZnO / KPHI composite photocatalyst includes the following steps: S1, weigh 3.000g of melamine and 9.000g of pure KCl molten salt, add them together to 30ml of deionized water, mix with magnetic stirring, and heat to 85℃, hold for 20min to homogenize the precursors. Then heat to 100℃ to completely evaporate the water, obtaining a solid mixture. Transfer the solid mixture to an agate grinding mortar for fine grinding, then place it in a covered ceramic crucible, put it in a box-type muffle furnace, heat to 580℃ at a heating rate of 4℃ / min, and calcine at that temperature for 2h. After the furnace has completely cooled to room temperature, remove it and wash it 5 times with deionized water and anhydrous ethanol by centrifugation to ensure that residual potassium chloride is removed. Dry it in a 60℃ vacuum drying oven, grind it, and collect the supercrystalline KPHI substrate.

[0029] S2, accurately weigh 0.0335g of anhydrous ZnCl2 solid and 1.9800g of KPHI substrate powder obtained in step S1, add them together to 10ml of deionized water, place in an ultrasonic cleaner and continuously ultrasonically disperse for 30min to allow protons and zinc ions to electrostatically adsorb between the KPHI layers, then transfer to a magnetic stirrer and maintain steady stirring for 30min; while maintaining high-speed stirring, slowly add 10mL of prepared NaOH solution dropwise to the above suspension through a microsyringe, adjusting the total molar ratio of NaOH to ZnCl2 to 4.8:1, and continue vigorous stirring for 30min after the addition is completed to obtain the reaction solution.

[0030] S3. Transfer the reaction solution from step S2 to a sealed reaction vessel and place it in a constant-temperature drying oven. Maintain a gentle, low-temperature reaction at 75°C for 22 hours. After the system has completely cooled to ambient temperature, collect the bottom precipitate by high-speed centrifugation. Wash and separate the precipitate four times with deionized water and anhydrous ethanol to thoroughly remove free Na. + and Cl - Ultimately, a 1% ZnO / KPHI composite photocatalyst with high specific surface area interfacial coupling was obtained.

[0031] Example 5 A method for preparing a ZnO / KPHI composite photocatalyst includes the following steps: S1, weigh 3.000g of melamine and 12.000g of pure KCl molten salt, add them together to 30ml of deionized water, mix with magnetic stirring, and heat to 95℃, hold for 40min to homogenize the precursors. Then heat to 100℃ to completely evaporate the water, obtaining a solid mixture. Transfer the solid mixture to an agate grinding mortar for fine grinding, then place it in a covered ceramic crucible, put it in a box-type muffle furnace, heat to 620℃ at a heating rate of 6℃ / min, and calcine at that temperature for 2.5h. After the furnace has completely cooled to room temperature, remove it and wash it five times with deionized water and anhydrous ethanol by centrifugation to ensure that residual potassium chloride is removed. Dry it in a 60℃ vacuum drying oven, grind it, and collect the supercrystalline KPHI substrate.

[0032] S2, accurately weigh 0.0335g of anhydrous ZnCl2 solid and 1.9800g of KPHI substrate powder obtained in step S1, add them together to 10ml of deionized water, place in an ultrasonic cleaner and continuously ultrasonically disperse for 40min to allow protons and zinc ions to electrostatically adsorb between the KPHI layers, then transfer to a magnetic stirrer and maintain steady stirring for 30min; while maintaining high-speed stirring, slowly add 10mL of prepared NaOH solution dropwise to the above suspension through a microsyringe, adjusting the total molar ratio of NaOH to ZnCl2 to 5.2:1, and continue vigorous stirring for 30min after the addition is completed to obtain the reaction solution.

[0033] S3. Transfer the reaction solution from step S2 to a sealed reaction vessel and place it in a constant-temperature drying oven. Maintain a gentle, low-temperature reaction at 85°C for 26 hours. After the system has completely cooled to ambient temperature, collect the bottom precipitate by high-speed centrifugation. Wash and separate the precipitate four times with deionized water and anhydrous ethanol to thoroughly remove free Na. + and Cl - Ultimately, a 1% ZnO / KPHI composite photocatalyst with high specific surface area interfacial coupling was obtained.

[0034] Comparative Example 1 Preparation of pure ZnO monomer control sample: Accurately weigh 0.0335 g of anhydrous ZnCl2 solid and completely dissolve it in 10 mL of deionized water. Without adding any KPHI substrate, add 10 mL of NaOH solution dropwise (molar ratio of NaOH:ZnCl2 = 5:1) while maintaining constant stirring. After vigorous stirring for 30 min, transfer to an 80℃ drying oven to maintain low-temperature precipitation and hydrolysis reaction for 24 h. After centrifugation, washing with water and alcohol, drying at 60℃, and grinding, obtain pure ZnO monomer particle control sample.

[0035] Experimental results verification: Figure 1a, b, and c are field emission scanning electron microscopy (FESEM) comparison images of the microstructures of KPHI, 3% ZnO / KPHI, and ZnO.

[0036] The performance evaluation of the in-situ total synthesis of H2O2 driven by full-spectrum photocatalysis was carried out by comparing the total synthesis performance of H2O2 in Example 1 (3% ZnO / KPHI), Example 2 (1% ZnO / KPHI), Example 3 (5% ZnO / KPHI), pure KPHI substrate and control Example 1 (pure ZnO).

[0037] Test Procedure: Accurately weigh 20 mg of each catalyst sample and uniformly suspend them in 80 mL of a mixed reaction solution prepared with 72 mL of deionized water and 8 mL of ethanol as a sacrificial agent. Disperse the mixture ultrasonically for 10 min to ensure no macroscopic agglomeration. Then transfer the entire mixture to a sealed three-necked glass reaction flask. Under dark conditions, continuously purge the reaction solution with high-purity O2 for 20 min to saturate dissolved oxygen and completely purge any residual air. Then turn on the high-power xenon lamp light source system, maintaining full-spectrum irradiation without filters. Adjust the vertical distance of the light source to 15 cm and fully initiate the photocatalytic oxygen reduction reaction while maintaining constant-speed magnetic stirring. After the light is activated, precisely extract 1 mL of the suspension every 15 min using a micropipette and centrifuge to completely remove catalyst particles. Extract the supernatant and add it to a pre-prepared system of potassium iodide (KI) and potassium hydrogen phthalate acidic characteristic colorimetric reagent. Allow the mixture to stand in the dark for 30 min for color development. The absorbance was measured at the characteristic wavelength using a UV-Vis spectrophotometer (UVmini-1280), and the quantitative accumulation of H2O2 was calculated by converting the absorbance-concentration standard curve.

[0038] Test Result Analysis: Depend on Figure 2The XRD patterns show that the diffraction peaks of the pure ZnO sample correspond perfectly to the standard card JCPDS No. 75-9742. The pure KPHI sample only shows its characteristic (002) diffraction peak at 2θ≈27°. The 3%, 5%, 10%, and 16.7% ZnO / KPHI composite samples all retain both the characteristic diffraction peaks of KPHI and ZnO, indicating that the preparation process of this invention can achieve stable composite of ZnO and KPHI without destroying the layered crystal structure of KPHI or generating impurity phases. No obvious ZnO diffraction peak was observed in the 3% ZnO / KPHI sample, indicating that ZnO at this loading level is relatively stable. The ZnO particles are highly uniformly dispersed between the KPHI layers, creating an interlayer spreading effect. As the ZnO loading increases to 5%, 10%, and 16.7%, the ZnO diffraction peaks become clearer and their intensity continuously increases, proving that ZnO grains agglomerate and grow under high loading conditions. This crystal structure change pattern is consistent with the change pattern of photocatalytic hydrogen peroxide production performance of each sample. From the perspective of phase crystallization, 3% confirms that the optimal ZnO loading of this invention is 3%. Excessive ZnO agglomeration can easily obscure the reactive active sites and intensify the recombination of photogenerated carriers. At the same time, the composite system can completely retain the inherent band structure advantage of KPHI adapted to the oxygen two-electron reduction reaction.

[0039] Depend on Figure 3 The high-resolution XPS spectra of KPHI, pure ZnO, 3% ZnO / KPHI under light-shielded conditions, and 3% ZnO / KPHI under illumination are shown in (a) C1s, (b) O1s, (c) N1s, (d) K2p, and (e) Zn2p. It can be seen that compared to single KPHI and pure ZnO samples, the binding energies of the characteristic peaks for C, N, and K elements in the light-shielded composite 3% ZnO / KPHI shift to higher values, while the binding energy of the characteristic peak for Zn element shifts to lower values. This proves that the KPHI-ZnO interface has a built-in electric field due to the difference in work function, causing electrons to spontaneously migrate from ZnO to KPHI; after illumination... After illumination, the binding energies of the characteristic peaks of each element in the 3%ZnO / KPHI-Light group underwent a reverse shift. The binding energies of C1s, N1s, and K2p on the KPHI side decreased, while the binding energy of Zn2p on the Zn side increased. At the same time, the proportion of the characteristic peak corresponding to adsorbed hydrogen peroxide in the O1s spectrum increased significantly. This reverse shift in binding energy before and after illumination directly confirms that the composite photocatalyst of this invention constructs an S-type heterojunction. Under illumination, low-reduction electrons in the ZnO conduction band recombine with low-oxidation holes in the KPHI valence band at the interface, and high-reduction-activity electrons are enriched in the KPHI conduction band to efficiently drive the two-electron reduction of oxygen to generate hydrogen peroxide.

[0040] The control group showed the following: Figure 4 As shown: In Control Example 1 (pure ZnO), due to the severe wide bandgap and rapid electron recombination, the amount of H2O2 generated within 60 minutes was almost negligible, only 0.37 mmol•g. -1Pure KPHI exhibited basic activity, with a yield of 5.40 mmol•g at 60 min. -1 .

[0041] The most significant leap in efficiency was observed in Example 1 (3% ZnO / KPHI), prepared using the process of this invention. This example exhibited the most impressive catalytic activity, with H2O2 production jumping to 11.97 mmol•g within 60 min. -1 The concentrations were 32.4 times that of single ZnO and 2.2 times that of pure KPHI, respectively.

[0042] Loading threshold effect: As the loading deviates from the optimal value, the yield in Example 2 (1% loading) drops to 6.69 mmol•g at 60 min due to insufficient heterogeneous interface. -1 In Example 3 (5% loading), the yield dropped to 5.88 mmol•g due to surface space shading and particle agglomeration caused by excessive ZnO. -1 This strongly demonstrates that the morphological expansion and S-shaped charge flow channels induced by the present invention at the optimal 3% loading level achieve a synergistic destructive balance.

[0043] Operational stability: The catalyst solid after the reaction in Example 1 was recovered by high-speed centrifugation, washed, dried, and then reintroduced into the next cycle of stability testing under the same conditions. Even after long-term light exposure, its H2O2 production remained robust at 10.72 mmol•g. -1 The overall activity retention rate is as high as 89.6%, demonstrating extremely strong resistance to passivation and deactivation over long industrial cycles.

[0044] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a ZnO / KPHI composite photocatalyst, characterized in that, Includes the following steps: S1, melamine and potassium chloride are dissolved in deionized water at a mass ratio of 1:3~4, mixed at 85~95℃ and kept at the temperature for 20~40 min, and the water is evaporated to obtain a solid mixture; the solid mixture is ground and heated to 580~620℃ at a heating rate of 4~6℃ / min, calcined at the constant temperature for 1.5~2.5 h, and after natural cooling, washed, dried and ground, KPHI substrate is obtained; S2, add anhydrous zinc chloride and KPHI base powder to deionized water, ultrasonically disperse for 20-40 min, add sodium hydroxide solution dropwise while stirring, control the molar ratio of NaOH to ZnCl2 to be 4.8-5.2:1, and continue stirring for 20-40 min after the sodium hydroxide solution is completely added to obtain the reaction solution; S3. The reaction solution was sealed and placed in an environment of 75~85℃ for 22~26h. After the reaction was completed, it was cooled to room temperature, centrifuged, washed, dried and ground to obtain a ZnO / KPHI composite photocatalyst with an S-shaped heterojunction.

2. The method for preparing a ZnO / KPHI composite photocatalyst according to claim 1, characterized in that: In step S2, the amount of KPHI added is adjusted so that the theoretical mass fraction of ZnO in the final composite photocatalyst is 1%~10%.

3. The method for preparing a ZnO / KPHI composite photocatalyst according to claim 2, characterized in that: In step S2, the theoretical mass fraction of ZnO in the final composite photocatalyst is 3% by adjusting the amount of KPHI added.

4. The method for preparing a ZnO / KPHI composite photocatalyst according to claim 3, characterized in that: In step S3, after sealing the reaction solution, it is transferred to a reaction vessel or a constant temperature drying oven and maintained in situ hydrolysis reaction at 80°C for 24 hours.

5. A ZnO / KPHI composite photocatalyst, characterized in that: The ZnO / KPHI composite photocatalyst is an S-type heterojunction photocatalyst and has a porous mesoporous morphology.

6. The ZnO / KPHI composite photocatalyst according to claim 5, characterized in that: The ZnO / KPHI composite photocatalyst was prepared according to any one of claims 1 to 4.

7. The ZnO / KPHI composite photocatalyst according to claim 5 is applied to the in-situ synthesis of hydrogen peroxide through visible light or full-spectrum driven oxygen two-electron reduction.

Images