Composite photocatalyst, preparation method and application thereof

Abstract

This application belongs to the field of environmental functional materials and air pollution technology, specifically relating to a composite photocatalyst, its preparation method, and its application. The composite photocatalyst includes Cd. x Zn 1‑x S and aluminum-doped strontium titanate, the Cd x Zn 1‑x S is grown in situ on the surface of aluminum-doped strontium titanate in the form of nanospheres, where x takes the value of 0.1-0.9. The beneficial effects of this application include: the composite photocatalyst described in this application, through the construction of Cd... x Zn 1‑x The tight heterostructure between S and Al-SrTiO3 forms oxygen bridges such as Cd-O-Sr and Zn-O-Ti, achieving strong chemical bonding and band matching at the interface. This structure effectively suppresses the recombination of photogenerated electron-hole pairs (significantly reducing the PL spectral signal), enhances the photocurrent response (stronger transient photocurrent), and reduces the interfacial resistance (smallest EIS arc radius), thereby significantly improving quantum efficiency. This is beneficial for the adsorption and activation of NH3 molecules and can effectively control the reaction pathway, inhibiting NO. x The generation of harmful byproducts increases the selectivity of the reaction.

Description

Technical Field

[0001] This application belongs to the field of environmental functional materials and air pollution technology, specifically relating to a composite photocatalyst, its preparation method, and its application. Background Technology

[0002] With the rapid development of intensive and large-scale livestock and poultry farming, the problem of odorous gas pollution from farms has become increasingly serious. Ammonia (NH3) is one of the most significant odorous pollutants in livestock sheds, manure treatment areas, and composting sites. NH3 not only strongly irritates the human respiratory tract and eyes, harming the health of farm workers and surrounding residents, but it also contributes to eutrophication of soil and water bodies through dry and wet deposition, forming PM2.5 in the atmosphere. 2.5 One of the important precursors of NH3. Therefore, efficient and economical purification of NH3 from livestock and poultry farming sources is of urgent practical significance.

[0003] Among numerous purification technologies, photocatalytic oxidation is considered one of the most promising green purification solutions due to its ability to directly degrade NH3 into harmless substances such as N2 and H2O at room temperature and pressure. However, the commercial application of this technology heavily relies on the development of high-performance photocatalysts, and existing photocatalysts still have significant shortcomings in terms of efficiency, spectral response range, and stability. Currently, the most widely studied photocatalyst is titanium dioxide (TiO2), whose photogenerated electron-hole pairs recombine rapidly, greatly reducing the carrier concentration participating in surface redox reactions, resulting in low apparent quantum efficiency. Consequently, the NH3 degradation rate cannot meet the treatment requirements of large-volume, high-concentration waste gas.

[0004] Currently, researchers have developed many novel photocatalysts, such as nitrogen-doped or sulfur-doped TiO2, g-C3N4, and Bi-based semiconductors. However, these photocatalysts generally suffer from insufficient conduction band positions and weak photogenerated hole oxidation capabilities, resulting in unsatisfactory efficiency for reactions requiring strong oxidizing agents to completely oxidize NH3. Furthermore, these materials are prone to photocorrosion in strong oxidizing environments, exhibiting poor stability. On the other hand, constructing heterojunctions (such as Type-II and Z-schemes) to promote carrier separation is an effective strategy for improving photocatalytic efficiency. However, traditional heterojunction interfaces often suffer from problems such as imperfect band matching, high interfacial resistance, and loose contact, leading to unsatisfactory carrier migration efficiency. Moreover, for the specific reaction of NH3 degradation, the surface properties of the catalyst, such as its adsorption capacity for NH3 molecules and the selectivity of the reaction pathway (controlling byproducts such as NO), are crucial factors. x The generation of [something], etc., has not yet been finely regulated.

[0005] In particular, in practical applications at livestock and poultry farms, to balance the needs of sterilization and deodorization, the wavelengths of the ultraviolet lamps used may include both sterilization bands (e.g., 253 nm) and long-wave ultraviolet (e.g., 365 nm). Therefore, developing a photocatalyst that maintains high efficiency and stable activity in both of these typical ultraviolet bands is crucial for designing general-purpose, high-efficiency odor purification equipment for livestock farms. In existing technologies, single-component or simply composite catalysts cannot simultaneously meet these requirements. Therefore, there is an urgent need in this field to develop a novel composite photocatalyst. Summary of the Invention

[0006] This application provides a composite photocatalyst, its preparation method, and its application, aiming to solve the problems of narrow spectral response and low efficiency of existing photocatalysts for ammonia degradation.

[0007] The first aspect of this application provides a composite photocatalyst, the composite photocatalyst comprising Cd x Zn 1-x S and aluminum-doped strontium titanate, the Cd x Zn 1-x S grows in situ on the surface of aluminum-doped strontium titanate in the form of nanospheres, where x ranges from 0.1 to 0.9.

[0008] According to some embodiments of the composite photocatalyst described in this application, Cd is grown in situ on the surface of aluminum-doped strontium titanate. x Zn 1-x The particle size of S nanospheres ranges from 10 to 40 nm; for example, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, etc.

[0009] According to some embodiments of the composite photocatalyst described in this application, the ultraviolet light absorption wavelength of the composite photocatalyst is 200-400 nm.

[0010] According to some embodiments of the composite photocatalyst described in this application, Cd in the composite photocatalyst x Zn 1-x The molar ratio of S to aluminum-doped strontium titanate is 1:(1.5-3).

[0011] According to some embodiments of the composite photocatalyst described in this application, the preparation raw materials include the following parts by weight: 5-8 parts of cadmium source, 5-9 parts of zinc source, 10-16 parts of sulfur source and 15-24 parts of aluminum-doped strontium titanate.

[0012] According to some embodiments of the composite photocatalyst described in this application, the molar ratio of cadmium in the cadmium source to zinc in the zinc source is 1:9-9:1.

[0013] According to some embodiments of the composite photocatalyst described in this application, the cadmium source includes cadmium acetate dihydrate and / or cadmium nitrate.

[0014] According to some embodiments of the composite photocatalyst described in this application, the zinc source includes zinc acetate dihydrate and / or zinc nitrate.

[0015] According to some embodiments of the composite photocatalyst described in this application, the sulfur source includes Na2S•9H2O.

[0016] A second aspect of this application provides a method for preparing the composite photocatalyst described in the first aspect of this application, comprising the following steps:

[0017] (1) Mix cadmium source, zinc source, aluminum-doped strontium titanate and solvent to obtain solution A; (2) Add a sulfur source to solution A and mix to react, and obtain the composite photocatalyst.

[0018] According to some embodiments of the preparation method of the composite photocatalyst described in this application, in step (1), the solvent includes water.

[0019] According to some embodiments of the preparation method of the composite photocatalyst described in this application, in step (1), the mixing temperature is 25-30℃ and the time is 30-60 min.

[0020] According to some embodiments of the preparation method of the composite photocatalyst described in this application, in step (2), the temperature of the mixing reaction is 180-205℃ and the time is 10-16h.

[0021] According to some embodiments of the preparation method of the composite photocatalyst described in this application, step (2) further includes filtering the reaction solution, collecting the solid product, washing with deionized water and drying the solid product to obtain the composite photocatalyst.

[0022] According to some embodiments of the preparation method of the composite photocatalyst described in this application, the drying temperature is 55-65°C.

[0023] The third aspect of this application provides the application of the composite photocatalyst described in the first aspect of this application or the composite photocatalyst prepared by the method described in the second aspect of this application in the degradation of ammonia.

[0024] The beneficial effects of this application include: the light absorption edge of the composite photocatalyst described in this application is red-shifted (~500nm), and it has strong absorption in the 200-400 nm ultraviolet region, possessing the characteristics of "broad band and high response".

[0025] The composite photocatalyst described in this application is constructed by Cd... x Zn 1-xThe tight heterostructure between S and Al-SrTiO3 forms oxygen bridges such as Cd-O-Sr and Zn-O-Ti, achieving strong chemical bonding and band matching at the interface. This structure effectively suppresses the recombination of photogenerated electron-hole pairs (significantly reducing the PL spectral signal), enhances the photocurrent response (stronger transient photocurrent), and reduces the interfacial resistance (smallest EIS arc radius), thereby significantly improving quantum efficiency. This is beneficial for the adsorption and activation of NH3 molecules and can effectively control the reaction pathway, inhibiting NO. x The generation of harmful byproducts increases the selectivity of the reaction.

[0026] The composite photocatalyst described in this application has strong interfacial chemical bonding, which gives it extremely high structural stability and overcomes the technical problems of photocorrosion and poor stability of many semiconductor materials (such as pure CdS) during photocatalysis.

[0027] The composite photocatalyst described in this application exhibits extremely high NH3 degradation efficiency (91.3% and 95.6% respectively) in two typical wavelength bands: 253nm (sterilizing ultraviolet) and 365nm (long-wave ultraviolet). This makes it directly compatible with the existing ultraviolet lamp system in the farm that combines sterilization and deodorization, without the need to replace the light source, and it has strong practicality.

[0028] The composite photocatalyst described in this application employs a two-step method of "solid-phase reaction and hydrothermal in-situ growth," which is simple and allows for controllable conditions. By adjusting the ratio of Cd / Zn precursors, the Cd content can be precisely controlled. x Zn 1-x The composition of S is optimized to improve its light absorption and catalytic performance, resulting in good repeatability and suitability for large-scale production. Attached Figure Description

[0029] Figure 1 This is a scanning electron microscope image of the composite photocatalyst described in Example 1 of this application; Figure 2 This is a scanning electron microscope image of the photocatalyst described in Comparative Example 1 of this application; Figure 3 This is a scanning electron microscope image of the photocatalyst described in Comparative Example 2 of this application; Figure 4 This is an elemental distribution (EDS) diagram of the composite photocatalyst described in Example 1 of this application; Figure 5 The UV-Vis absorption spectra of the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application are shown. Figure 6 The XRD patterns of the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application are shown below. Figure 7XPS analysis images of the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application; Figure 8 The photoluminescence spectra of the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application are shown. Figure 9 The transient photocurrent response diagrams are for the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application. Figure 10 The electrochemical impedance spectroscopy (EIS) spectra of the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application are shown. Figure 11 The images show the photocatalytic degradation effect of the composite photocatalysts described in Examples 1-5 and Comparative Examples 1-2 of this application on ammonia gas at 365 nm. Figure 12 The images show the photocatalytic degradation effect of ammonia gas at 253 nm using the composite photocatalysts described in Examples 1-5 and Comparative Examples 1-2 of this application. Figure 13 The UV-Vis absorption spectra of the composite photocatalysis described in Examples 1-5 of this application are shown. Figure 14 The graphs show the changes in NH3 degradation efficiency under 365nm ultraviolet light irradiation for the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application. Figure 15 C obtained in Embodiment 1 of this application 0.5 Z 0.5 Catalytic effect diagram of S-ASTO sample being repeatedly recycled. Detailed Implementation

[0030] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0031] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0032] This application provides a composite photocatalyst, the composite photocatalyst comprising Cd x Zn1-x S and aluminum-doped strontium titanate, the Cd x Zn 1-x S grows in situ on the surface of aluminum-doped strontium titanate in the form of nanospheres, where x ranges from 0.1 to 0.9.

[0033] The composite photocatalyst described in this application is constructed by Cd... x Zn 1-x The tight heterostructure between S and Al-SrTiO3 forms oxygen bridges such as Cd-O-Sr and Zn-O-Ti, achieving strong chemical bonding and band matching at the interface. This structure effectively suppresses the recombination of photogenerated electron-hole pairs (significantly reducing the PL spectral signal), enhances the photocurrent response (stronger transient photocurrent), and reduces the interfacial resistance (smallest EIS arc radius), thereby significantly improving quantum efficiency. This is beneficial for the adsorption and activation of NH3 molecules and can effectively control the reaction pathway, inhibiting NO. x The generation of harmful byproducts increases the selectivity of the reaction.

[0034] In some embodiments of this application, Cd is grown in situ on the surface of aluminum-doped strontium titanate. x Zn 1-x The particle size of the S nanospheres is 10-40 nm.

[0035] In some embodiments of this application, the ultraviolet light absorption wavelength of the composite photocatalyst is 200-400 nm. The composite photocatalyst described in this application possesses "broad bandgap and high response" characteristics, and can be directly adapted to existing ultraviolet lamp systems in farms that combine sterilization and deodorization, without requiring replacement of the light source, thus exhibiting strong practicality. The composite photocatalyst described in this application demonstrates strong absorption capacity in the 200-400 nm ultraviolet light range and has high efficiency response to both typical ultraviolet bands of 253 nm and 365 nm, exhibiting dual-band high-efficiency catalytic capability.

[0036] In some embodiments of this application, the composite photocatalyst contains Cd x Zn 1-x The molar ratio of S to aluminum-doped strontium titanate is 1:(1.5-3).

[0037] In some embodiments of this application, the preparation raw materials include the following parts by weight: 5-8 parts of cadmium source, 5-9 parts of zinc source, 10-16 parts of sulfur source and 15-24 parts of aluminum-doped strontium titanate.

[0038] In some embodiments of this application, the molar ratio of cadmium in the cadmium source to zinc in the zinc source is 1:9-9:1.

[0039] In some embodiments of this application, the cadmium source includes cadmium acetate dihydrate and / or cadmium nitrate; In some embodiments of this application, the zinc source includes zinc acetate dihydrate and / or zinc nitrate; In some embodiments of this application, the sulfur source includes Na2S•9H2O.

[0040] This application also provides a method for preparing the composite photocatalyst described in the first aspect of this application, comprising the following steps: (1) Mix cadmium source, zinc source, aluminum-doped strontium titanate and solvent to obtain solution A; (2) Add a sulfur source to solution A and mix to react, to obtain the composite photocatalyst, denoted as Cd. x Zn 1-x S-ASTO.

[0041] The composite photocatalyst described in this application employs a two-step method of "solid-phase reaction and hydrothermal in-situ growth," which is simple and allows for controllable conditions. By adjusting the ratio of Cd / Zn precursors, the Cd content can be precisely controlled. x Zn 1-x The composition of S is optimized to improve its light absorption and catalytic performance, resulting in good repeatability and suitability for large-scale production.

[0042] In some embodiments of this application, in step (1), the solvent includes water.

[0043] In some embodiments of this application, in step (1), the mixing temperature is 25-30°C and the time is 30-60 min. First, the cadmium source, zinc source, and aluminum-doped strontium titanate are mixed so that cadmium ions and zinc ions are adsorbed on the surface of aluminum-doped strontium titanate and fully dispersed. After adding the sulfur source, zinc-sulfur cadmium is generated in situ. The zinc-sulfur cadmium obtained in this way is fully dispersed on the surface of aluminum-doped strontium titanate, tightly bound, not easy to agglomerate, which is conducive to the migration of photogenerated electrons and holes.

[0044] In some embodiments of this application, in step (2), the temperature of the mixing reaction is 180-205℃, such as 180℃, 186℃, 193℃, 198℃, 200℃, 205℃, etc., and the time is 10-16h, such as 10h, 12h, 15h, 16h, etc.

[0045] In some embodiments of this application, step (2) further includes filtering the reaction solution, collecting the solid product, washing with deionized water and drying the solid product to obtain the composite photocatalyst.

[0046] In some embodiments of this application, the drying temperature is 55-65°C, such as 55°C, 58°C, 60°C, 62°C, 65°C, etc.

[0047] In some embodiments of this application, the method for preparing aluminum-doped strontium titanate includes the following steps: a. Mix SrCl2, Al2O3, and SrTiO3 in a molar ratio of (8-11):(0.015-0.025):1 and grind them in an agate mortar for 30 minutes to obtain a mixture of the three. Place the mixture in an alumina crucible and calcine it in a muffle furnace (air atmosphere) at 1100-1200℃ for 8-12 hours. b. After the calcined product has cooled naturally to room temperature, collect the solid product in the alumina crucible and wash it three times with deionized water to remove residual SrCl2. c. Place the washed solid product in an oven and dry it at 60°C to obtain powdered aluminum-doped strontium titanate, denoted as ASTO.

[0048] This application also provides an application of the composite photocatalyst described in the first aspect of this application or the composite photocatalyst prepared by the method described in the second aspect of this application in the degradation of ammonia. The composite photocatalyst described in this application facilitates the adsorption and activation of NH3 molecules and can effectively control the reaction pathway, inhibiting NO... x The generation of harmful byproducts increases the selectivity of the reaction.

[0049] The technical solution of this application will be further described below with reference to specific embodiments.

[0050] Example 1 A method for preparing a composite photocatalyst includes the following steps: (1) Mix SrCl2, Al2O3 and SrTiO3 in a molar ratio of 10:0.02:1 and grind them in an agate mortar for 30 min to obtain a mixture of the three. Place the mixture in an alumina crucible and calcine it in a muffle furnace (air atmosphere) at 1150℃ for 10 h. After the calcined product cools naturally to room temperature, collect the solid product in the alumina crucible and wash it three times with deionized water to remove residual SrCl2. Place the washed solid product in an oven and dry it at 60℃ to obtain powdered aluminum-doped strontium titanate, denoted as ASTO.

[0051] (2) Add 0.066g of cadmium acetate dihydrate and 0.0548g of zinc acetate dihydrate to 20mL of deionized water and stir at 25℃ for 30min to obtain solution A; add 0.184g of ASTO to solution A and stir at 25℃ for 30min to obtain suspension B; (3) Add 0.12g of Na2S•9H2O to 10mL of deionized water and stir at 25℃ for 30min to obtain solution C; add solution C to suspension B and stir for 30min to obtain mixture D; (4) Add mixture D to a 50 mL reaction vessel with a Teflon liner and place it in an oven at 200 °C for 12 h. After the reaction is complete, allow the reactants to cool naturally to room temperature, collect the solid product in the reaction vessel, and wash it three times with deionized water. Place the washed solid product in an oven and dry it at 60 °C to obtain powdered zinc cadmium sulfide / aluminum doped strontium titanate composite photocatalyst, denoted as Cd. 0.5 Zn 0.5 S-ASTO, abbreviated as C 0.5 Z 0.5 S-ASTO.

[0052] Example 2 The only difference between the preparation method of the composite photocatalyst in Example 2 and that in Example 1 is that the amounts of cadmium acetate dihydrate and zinc acetate dihydrate used in the preparation process of the composite photocatalyst in Example 2 are different from those in Example 1.

[0053] The specific operating steps include: (2) Add 0.0132 g of cadmium acetate dihydrate and 0.09864 g of zinc acetate dihydrate to 20 mL of deionized water and stir for 30 min to obtain solution A; add 0.184 g of ASTO to solution A and stir for 30 min to obtain suspension B; the remaining operation steps are the same as in Example 1. The obtained composite photocatalyst is denoted as Cd. 0.1 Zn 0.9 S-ASTO catalyst, abbreviated as C 0.1 Z 0.9 S-ASTO.

[0054] Example 3 The only difference between the preparation method of the composite photocatalyst in Example 3 and that in Example 1 is that the amounts of cadmium acetate dihydrate and zinc acetate dihydrate used in the preparation process of the composite photocatalyst in Example 3 are different from those in Example 1.

[0055] The specific operating steps include: (2) Add 0.0396 g of cadmium acetate dihydrate and 0.07672 g of zinc acetate dihydrate to 20 mL of deionized water and stir for 30 min to obtain solution A; add 0.184 g of ASTO to solution A and stir for 30 min to obtain suspension B; the remaining operation steps are the same as in Example 1. The obtained composite photocatalyst is denoted as Cd. 0.3 Zn 0.7 S-ASTO catalyst, abbreviated as C 0.3 Z 0.7 S-ASTO.

[0056] Example 4 The only difference between the preparation method of the composite photocatalyst in Example 4 and that in Example 1 is that the amounts of cadmium acetate dihydrate and zinc acetate dihydrate used in the preparation process of the composite photocatalyst in Example 4 are different from those in Example 1.

[0057] The specific operating steps include: (2) Add 0.0924 g of cadmium acetate dihydrate and 0.03288 g of zinc acetate dihydrate to 20 mL of deionized water and stir for 30 min to obtain solution A; add 0.184 g of ASTO to solution A and stir for 30 min to obtain suspension B; the remaining operation steps are the same as in Example 1. The obtained composite photocatalyst is denoted as Cd. 0.7 Zn 0.3 S-ASTO catalyst, abbreviated as C 0.7 Z 0.3 S-ASTO.

[0058] Example 5 The only difference between the preparation method of the composite photocatalyst in Example 5 and that in Example 1 is that the amounts of cadmium acetate dihydrate and zinc acetate dihydrate used in the preparation process of the composite photocatalyst in Example 5 are different from those in Example 1.

[0059] The specific operating steps include: (2) Add 0.1188 g of cadmium acetate dihydrate and 0.01096 g of zinc acetate dihydrate to 20 mL of deionized water and stir for 30 min to obtain solution A; add 0.184 g of ASTO to solution A and stir for 30 min to obtain suspension B; the remaining operation steps are the same as in Example 1. The obtained composite photocatalyst is denoted as Cd. 0.9 Zn 0.1 S-ASTO catalyst, abbreviated as C 0.9 Z 0.1 S-ASTO.

[0060] Example 6 The only difference between the preparation method of the composite photocatalyst described in Example 6 and that in Example 1 is that, in step (4) of the preparation process of the composite photocatalyst described in Example 6, the mixture D is placed in an oven and reacted at a temperature of 180°C.

[0061] Example 7 The only difference between the preparation method of the composite photocatalyst in Example 7 and that in Example 1 is that, in step (4) of the preparation process of the composite photocatalyst in Example 7, the mixture D is placed in an oven and reacted at a temperature of 190°C.

[0062] Example 8 The only difference between the preparation method of the composite photocatalyst described in Example 8 and that in Example 1 is that, in step (4) of the preparation process of the composite photocatalyst described in Example 8, the mixture D is placed in an oven and reacted at a temperature of 205°C.

[0063] Comparative Example 1 The only difference between the preparation method of the photocatalyst in Comparative Example 1 and Example 1 is that Comparative Example 1 uses aluminum-doped strontium titanate as the photocatalyst, denoted as ASTO.

[0064] Comparative Example 2 The only difference between the preparation method of the photocatalyst described in Comparative Example 2 and that in Example 1 is that no raw material ASTO is added during the preparation of the composite photocatalyst described in Comparative Example 2, and the rest of the operations are the same as in Example 1.

[0065] The specific operating steps include: (1) Add 0.066g of cadmium acetate dihydrate and 0.0548g of zinc acetate dihydrate to 20mL of deionized water and stir for 30min to obtain solution A; add 0.12g of Na2S•9H2O to 10mL of deionized water and stir for 30min to obtain solution C; add solution C to solution A and stir for 30min to obtain mixture D; (2) Add mixture D to a 50 mL reaction vessel with a Teflon liner and place it in an oven at 200 °C for 12 h. After the reaction is complete, allow the reactants to cool naturally to room temperature, collect the solid product in the reaction vessel, and wash it three times with deionized water. Place the washed solid product in an oven and dry it at 60 °C to obtain powdered zinc cadmium sulfide composite photocatalyst, denoted as Cd. 0.5 Zn 0.5 S, abbreviated as C 0.5 Z 0.5 S.

[0066] Comparative Example 3 The only difference between the preparation method of the composite photocatalyst described in Comparative Example 3 and Example 1 is that the order of adding Na2S•9H2O during the preparation of the composite photocatalyst described in Comparative Example 3 is different from that in Example 1.

[0067] The specific operating steps include: (2) Add 0.066g of cadmium acetate dihydrate and 0.0548g of zinc acetate dihydrate to 20mL of deionized water and stir for 30min to obtain solution A; add 0.184g of ASTO and 0.12g of Na2S•9H2O to solution A and stir for 30min to obtain solution B; (2) Add solution B to a 50 mL reaction vessel with a Teflon liner and place it in an oven at 200 °C for 12 h. After the reaction is complete, allow the reactants to cool naturally to room temperature, collect the solid product in the reaction vessel, and wash it three times with deionized water. Place the washed solid product in an oven and dry it at 60 °C to obtain the powdered composite photocatalyst.

[0068] 1. Scanning electron microscope (SEM) images of the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application are shown below. Figure 1 , Figure 2 and Figure 3 As shown.

[0069] from Figures 1 to 3 As can be seen from the morphology diagram of the composite photocatalyst described in this application, C... 0.5 Z 0.5 S grows relatively uniformly on the surface of cubic ASTO with spheres of about 30 nm, indicating strong chemical bonding at the interface rather than simple physical adsorption. C 0.5 Z 0.5 The severe clustering phenomenon of S is greatly reduced, and these particles provide a large number of surface reaction active sites for composite catalysts, which helps to promote the improvement of photocatalytic activity; The morphology image of ASTO prepared in Comparative Example 1 shows that ASTO exhibits a smooth cubic structure, which provides a rigid substrate and oriented lattice-matched interface for the growth of zinc cadmium sulfide (CZS) on it; the morphology image of CZS prepared in Comparative Example 2 shows that ASTO exhibits a smooth cubic structure, which provides a rigid substrate and oriented lattice-matched interface for the growth of zinc cadmium sulfide (CZS); 0.5 Z 0.5 The morphology diagram of S shows that it agglomerates into micron-sized clusters through van der Waals forces. This cluster structure can lead to the masking of reactive sites. The active sites on the catalyst surface are covered by adjacent particles, and the carrier migration needs to cross multiple grain boundaries, which in turn hinders its transport.

[0070] The elemental distribution (EDS) diagram of the composite photocatalyst described in Example 1 of this application is as follows: Figure 4 As shown.

[0071] from Figure 4 As can be seen, Sr, O, Ti, and Al elements are uniformly distributed across the entire cubic surface, indicating that the hydrothermal preparation process did not alter the elemental distribution of ASTO. This further demonstrates that ASTO not only maintains its original cubic shape in morphology but also maintains stability in atomic arrangement, providing a reliable substrate for the in-situ growth of CZS nanoparticles. Furthermore, the uniform distribution of Zn, Cd, and S on the cubic surface confirms that C... 0.5 Z 0.5 Successful synthesis of S-ASTO.

[0072] The UV-Vis absorption spectra of the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application are as follows: Figure 5 As shown.

[0073] from Figure 5 As can be seen from the above, the light absorption band edge of the composite photocatalyst described in Example 1 and Comparative Examples 1-2 of this application gradually red-shifts in the following order: ASTO <C 0.5 Z 0.5 S-ASTO <C 0.5 Z 0.5 The optical absorption band edge of S,ASTO is around 400nm, C 0.5 Z 0.5 The optical absorption band edge of S is around 550nm, and C... 0.5 Z 0.5 The optical absorption band edge of S-ASTO is around 500 nm; in addition, C 0.5 Z 0.5 S-ASTO exhibits strong absorption of light with wavelengths of 200-400 nm, demonstrating a wide spectral band and high response.

[0074] The XRD spectra of the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application are as follows: Figure 6 so.

[0075] from Figure 6 As can be seen from this: C described in Embodiment 1 of this application 0.5 Z 0.5 The XRD spectrum of S-ASTO is C 0.5 Z 0.5 The superposition of the XRD spectra of S and ASTO confirms that C 0.5 Z 0.5 S-ASTO is composed of C 0.5 Z 0.5 S and ASTO form a heterogeneous structure. To further reveal the chemical interactions between the composite materials, ASTO and C were separately analyzed. 0.5 Z 0.5 S, C 0.5 Z 0.5 S-ASTO underwent XPS analysis, and the results are as follows: Figure 7 As shown.

[0076] from Figure 7 It can be seen that: (To explain the changes in elemental binding energies in XPS, it is first necessary to clarify the electronegativity of the elements involved in this application: O is 3.44, S is 2.58, Sr is 0.95, titanium is 1.54, Zn is 1.65, Cd is 1.69, and Al is 1.61. Generally speaking, atoms with higher electronegativity have a stronger attraction to electrons). Figure 7 As shown in a, C0.5 Z 0.5 The doublet of Cd 3d in S is 411.99 eV / 405.26 eV, and in C 0.5 Z 0.5 The shift of 0.13 eV in the S-ASTO direction toward higher binding energy indicates a decrease in electron density around Cd. This may be due to the formation of oxygen bridge bonds such as Cd-O-Sr between Cd and O and Sr in the ASTO, with the high electronegativity of O attracting electrons around Cd. As shown in 7b, the pair of bimodals of Zn 2p are formed by C 0.5 Z 0.5 The S value increases from 1045.24 eV / 1022.18 eV to C. 0.5 Z 0.5 The 1045.46 eV / 1022.36 eV of S-ASTO may be due to the formation of Zn-O-Ti oxygen bridge bonds between Zn and O and Ti in ASTO. The high electronegativity of O attracts electrons from Zn, resulting in a decrease in the electron cloud density around Zn. like Figure 7 As shown in c, C 0.5 Z 0.5 The double peaks of S 2p in S are 162.95 eV / 161.73 eV, which is typical for S. 2- The characteristic signal of C can be seen. 0.5 Z 0.5 The binding energy of S in S-ASTO is slightly increased. This may be because S forms an oxygen bridge bond SO-Sr, and electrons are extracted by the highly electronegative oxygen atom, making the coordination environment of sulfur more complete. The electron cloud of sulfur is shared more evenly by the surrounding atoms, resulting in an increase in the overall binding energy. like Figure 7 The binding energy of Sr 3d in ASTO shown in Figure d corresponds to Sr 2+ The state in SrTiO3, in C 0.5 Z 0.5 The S-ASTO binding energy increased by 0.17 eV, indicating that SO-Sr bonds may form on the sulfide surface during hydrothermal processes, and Sr electrons also shift towards O, resulting in a decrease in the surrounding electron cloud density and thus an increase in binding energy. In C 0.5 Z 0.5 The Sr 3d peak of S-ASTO also shows a peak of 139.87 eV, indicating that Sr is directly bonded to S, forming an Sr-S or Sr-SOx structure. The high electronegativity of S attracts electrons from Sr to form Sr... + δ-S - δ-strong polar bond; like Figure 7 As shown in Figure e, the 464.00 eV / 458.30 eV peaks of Ti 2p in ASTO correspond to Ti 4+The state in SrTiO3. In C 0.5 Z 0.5 The binding energy of Ti 2p in S-ASTO shifts significantly to higher energy levels, approximately 0.4 eV. This also indicates the presence of oxygen-bridged Ti-O-Zn / Cd bonds, leading to a substantial decrease in the electron cloud density around Ti. Figure 7 In the ASTO shown in f, the 529.41 eV peak belongs to the lattice oxygen of ASTO, and the 531.8 eV peak is Al doped. 3+ Replace Ti 4+ The signal of formed oxygen vacancies. In C 0.5 Z 0.5 In S-ASTO, the 529.9 eV peak represents the lattice oxygen of SrTiO3, showing a slight shift compared to ASTO. This is due to the interaction between Zn / Cd atoms in the Zn-O-Ti and Cd-O-Sr bonds at the composite material interface and the SrTiO3 lattice, altering the local electronic environment of the lattice oxygen. The 531.0 eV peak represents the SO bond formed at the interface between zinc cadmium sulfide and strontium titanate, leading to a change in the oxygen coordination environment. The 532.3 eV peak may be due to oxygen-containing groups on the catalyst surface: the formation of SO bonds during hydrothermal processes and the increase in active sites result in an increase in the adsorption of H2O or -OH groups on the composite material surface.

[0077] The photoluminescence spectra of the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application are as follows: Figure 8 As shown.

[0078] from Figure 8 As can be seen from the data, the ASTO fluorescence signal is the strongest in the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application, indicating that severe carrier recombination occurred in these samples. (The last sentence appears to be incomplete and possibly contains errors.) 0.5 Z 0.5 After S combines, C 0.5 Z 0.5 The fluorescence signal of S-ASTO decreased significantly, indicating that severe carrier recombination in ASTO was effectively suppressed due to the formation of heterojunctions between them.

[0079] The transient photocurrent response diagrams of the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application are as follows: Figure 9 As shown.

[0080] from Figure 9 As can be seen from this, ASTO exhibits a very weak photocurrent response, which can be attributed to its wide bandgap and severe carrier recombination; C 0.5 Z 0.5 S has a narrow bandgap, therefore it exhibits a higher photocurrent response; compared with C 0.5 Z 0.5 Compared to S, C0.5 Z 0.5 The photocurrent response of S-ASTO is further enhanced, which means that severe carrier recombination is alleviated due to the formation of the heterojunction.

[0081] The electrochemical impedance spectroscopy (EIS) spectra of the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application are as follows: Figure 10 As shown.

[0082] from Figure 10 It can be seen that: C 0.5 Z 0.5 The smallest radius of the Nyquist curve for S-ASTO indicates its lowest electrochemical impedance, which is beneficial for the migration of photogenerated carriers. The above test results confirm that C... 0.5 Z 0.5 The formation of a heterojunction between S and ASTO effectively reduces the recombination of photogenerated carriers, improves their separation and migration, and ultimately contributes to improving C. 0.5 Z 0.5 S-ASTO photocatalytic performance.

[0083] 2. Performance study of the photocatalytic degradation of ammonia by the composite photocatalysts described in Examples 1-5 and Comparative Examples 1-2 of this application. 2.1 20 mg of the composite photocatalysts described in Examples 1-5 and Comparative Examples 1-2 of this application were ultrasonically dispersed in 5 mL of ethanol, then drop-coated onto the bottom surface of an inverted circular beaker with a radius of 2 cm and thoroughly dried to obtain a reaction system with the catalyst powder evenly spread. A mixture of ammonia / nitrogen (0.5% + 99.5%) and air were introduced into the reaction system using a mass flow meter for 30 min to ensure a constant ammonia concentration. The ammonia concentration was set to 90 ppm by adjusting the mass flow meter. During the photocatalysis process, the samples were irradiated with ultraviolet light at wavelengths of 253 nm and 365 nm, respectively, with a light source power of 220 W. A circulating cooling water system was used to maintain the system temperature at 25°C. The ammonia concentration after photocatalysis was monitored using an NH3 detector at 20-min intervals. The concentrations of nitric oxide (NO) and nitrogen dioxide (NO2) in the gas after photocatalysis were detected using a flue gas analyzer. The degradation efficiency of NH3 by seven samples after 2 hours of 365nm ultraviolet light irradiation is as follows: Figure 11 As shown.

[0084] from Figure 11 As can be seen from the data, the degradation efficiencies of the composite photocatalysts described in Examples 1-5 of this application are 95.6%, 60.3%, 85.6%, 79.5%, and 68.8%, respectively. The composite photocatalyst described in Example 1 exhibits superior catalytic degradation performance compared to Examples 2-5. It can be concluded that the degradation efficiency of Cd... 0.1 Zn 0.9The optimal molar ratio of Cd to Zn in the S-ASTO catalyst is 1:1, and a molar ratio of (3-7):(7-3) is preferred.

[0085] Comparing Examples 1 and 6-8, it can be seen that the degradation efficiencies of the composite photocatalysts described in Examples 6-8 are 80.1%, 86.1%, and 81.5%, respectively. That is, the composite photocatalyst described in Example 1 has better catalytic degradation performance than that described in Examples 6-8. It can be concluded that the composite catalyst obtained at a reaction temperature of 190-200℃ has better performance.

[0086] Comparing Example 1 and Comparative Examples 1-3, it can be seen that the degradation efficiencies of the composite photocatalysts described in Comparative Examples 1-3 are 10.3%, 45.3%, and 53.4%, respectively. The composite photocatalyst described in Example 1 exhibits the best photocatalytic NH3 degradation efficiency, which is much higher than that of single ASTO and single C. 0.5 Z 0.5 S indicates that the formation of a heterojunction between zinc cadmium sulfide and aluminum-doped strontium titanate significantly improves the photocatalytic performance; the photocatalytic NH3 degradation efficiency of the composite photocatalyst described in Example 1 is higher than that of Comparative Example 3, indicating that the in-situ growth of zinc cadmium sulfide on aluminum-doped strontium titanate surface helps to improve the photocatalytic performance of the catalyst.

[0087] 2.2 Based on the above test method, the 365nm ultraviolet light was changed to 253nm ultraviolet light, while other conditions remained unchanged. The degradation efficiency of NH3 by the composite photocatalysts described in Examples 1-5 and Comparative Examples 1-2 of this application was further tested, and the results are as follows: Figure 12 As shown.

[0088] from Figure 12 As can be seen, the degradation efficiencies of the composite photocatalysts described in Examples 1-5 and Comparative Examples 1-2 of this application are 91.3%, 55.9%, 72.6%, 73.1%, 60.7%, 9.1%, and 40.2%, respectively. These efficiencies are all slightly lower than the corresponding values ​​for ultraviolet light at 365 nm. This can be attributed to the difference in absorption of light of two different wavelengths by the samples.

[0089] 2.3 UV-Vis absorption spectra of the composite photocatalysts described in Examples 1-5 of this application from Figure 13 As can be seen, as x increases from 0.1 to 0.9, the absorption band edge of the series of samples gradually red-shifts, absorbing more visible light, and a trough appears at 253 nm, with its absorbance being significantly less than that at 365 nm.

[0090] 2.4 The curves showing the changes in NH3 degradation efficiency under 365nm ultraviolet light irradiation for the composite photocatalysts described in Example 1 and Comparative Examples 1-2 of this application are as follows: Figure 14 As shown.

[0091] from Figure 14 It can be seen that: a single ASTO and a single C 0.5 Z 0.5 S has low photocatalytic activity, and after they form a heterojunction, C 0.5 Z 0.5 The photocatalytic degradation efficiency of S-ASTO is significantly improved because the formation of the heterojunction promotes the effective separation of photogenerated electrons.

[0092] 2.5 Regarding the C obtained in Embodiment 1 of this application 0.5 Z 0.5 The S-ASTO samples were repeatedly cycled, with each cycle consisting of a 2-hour illumination period, for a total of six cycles, to assess their photocatalytic stability. The results are as follows: Figure 15 As shown.

[0093] from Figure 15 As can be seen from this: C described in Embodiment 1 of this application 0.5 Z 0.5 S-ASTO showed no significant decrease in photocatalytic performance during six cycles of photodegradation testing, demonstrating good stability. Furthermore, we investigated the C... 0.5 Z 0.5 The gas after 2 hours of S-ASTO photocatalytic reaction is subjected to NO... x The detection showed no formation of NO or NO2, indicating that the catalyst exhibits excellent selectivity. This may be because specific structures such as oxygen bridges formed on the catalyst surface facilitate the adsorption and activation of NH3 molecules and effectively control the reaction pathway, inhibiting NO formation. x The generation of harmful byproducts increases the selectivity of the reaction.

[0094] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A composite photocatalyst, characterized in that, The composite photocatalyst includes Cd x Zn 1-x S and aluminum-doped strontium titanate, the Cd x Zn 1-x S grows in situ on the surface of aluminum-doped strontium titanate in the form of nanospheres, where x ranges from 0.1 to 0.

9.

2. The composite photocatalyst according to claim 1, characterized in that, Cd grown in situ on the surface of aluminum-doped strontium titanate x Zn 1-x The particle size of S nanospheres is 10-40 nm; And / or, the ultraviolet light absorption wavelength of the composite photocatalyst is 200-400 nm; And / or, the Cd in the composite photocatalyst x Zn 1-x The molar ratio of S to aluminum-doped strontium titanate is 1:(1.5-3).

3. The composite photocatalyst according to claim 1, characterized in that, The preparation materials include the following parts by weight: 5-8 parts cadmium source, 5-9 parts zinc source, 10-16 parts sulfur source and 15-24 parts aluminum-doped strontium titanate.

4. The composite photocatalyst according to claim 3, characterized in that, The molar ratio of cadmium in the cadmium source to zinc in the zinc source is 1:9-9:

1.

5. The composite photocatalyst according to claim 3, characterized in that, The cadmium source includes cadmium acetate dihydrate and / or cadmium nitrate; And / or, the zinc source includes zinc acetate dihydrate and / or zinc nitrate; And / or, the sulfur source includes Na2S•9H2O.

6. The method for preparing the composite photocatalyst according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Mix cadmium source, zinc source, aluminum-doped strontium titanate and solvent to obtain solution A; (2) Add a sulfur source to solution A and mix to react, and obtain the composite photocatalyst.

7. The method for preparing the composite photocatalyst according to claim 6, characterized in that, In step (1), the solvent includes water; And / or, in step (1), the mixing temperature is 25-30°C and the time is 30-60 min.

8. The method for preparing the composite photocatalyst according to claim 6, characterized in that, In step (2), the temperature of the mixing reaction is 180-205℃ and the time is 10-16h.

9. The method for preparing the composite photocatalyst according to claim 6, characterized in that, Step (2) also includes filtering the reaction solution, collecting the solid product, washing the solid product with deionized water and drying the solid product to obtain the composite photocatalyst; Preferably, the drying temperature is 55-65°C.

10. The application of the composite photocatalyst according to any one of claims 1-5 or the composite photocatalyst obtained by the preparation method according to any one of claims 6-9 in the degradation of ammonia.

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