Perovskite composite photocatalyst for photocatalytic ethanol dehydrogenation and application

Abstract

The invention belongs to the field of photocatalysis, and particularly discloses a perovskite composite photocatalyst for photocatalytic ethanol dehydrogenation and application. The composite photocatalyst takes a CdS nanorod as a carrier, a Cs2AgBiBr6 double perovskite active component formed by CsBr, AgBr and BiBr3 precursors is loaded on the surface of the CdS nanorod through a vacuum in-situ growth method, and a Pt, Rh or Ni metal cocatalyst can be further loaded. The method comprises the following steps: dispersing a CdS nanorod and a perovskite precursor in a mixed organic solvent, carrying out vacuum freezing-air exhaust circulation treatment, and removing the solvent under a heating condition to prepare the composite photocatalyst. When the photocatalyst is used for an ethanol photocatalytic dehydrogenation reaction under an anaerobic condition, hydrogen, acetaldehyde and acetal can be efficiently generated under the irradiation of visible light. According to the method, the photo-generated charge separation efficiency and the reaction stability are remarkably improved, and a new way is provided for ethanol high-valued conversion.

Description

Technical Field

[0001] This invention relates to the field of photocatalysis technology, and specifically discloses a perovskite composite photocatalyst for photocatalytic ethanol dehydrogenation and its application. Background Technology

[0002] Ethanol, as an abundant and renewable resource, has long been a hot topic in scientific research regarding its chemical transformation pathways and efficient utilization strategies. Acetaldehyde, as a key product of ethanol dehydrogenation, has attracted considerable attention due to its wide application in various industries such as chemical synthesis and pharmaceutical manufacturing. However, traditional ethanol dehydrogenation processes typically face numerous challenges, including significant energy consumption, insufficient catalyst activity and selectivity, and severe environmental pollution. These problems severely restrict the economic efficiency and sustainability of acetal production. Therefore, exploring and developing a new, highly efficient, and environmentally friendly ethanol dehydrogenation process to achieve the efficient preparation of acetal is particularly urgent and important.

[0003] In recent years, with the increasing global emphasis on green chemistry and sustainable development, photocatalysis technology, with its unique green and energy-saving advantages, has gradually become a potential approach to solving these problems. Against this backdrop, halide perovskite materials, as an emerging photocatalyst, have shown remarkable application prospects in the field of photocatalysis due to their excellent photoelectric conversion efficiency, good chemical stability, and tunable optical properties. Halide perovskites can not only effectively utilize the broad spectral range of sunlight, but their unique crystal structure also facilitates efficient charge separation and transport, thus potentially improving the efficiency and selectivity of photocatalytic reactions. Although some progress has been made in the application research of halide perovskites in the field of photocatalysis, the octahedral framework of traditional perovskites faces fundamental problems such as bond length distortion and a reduction in phase transition energy barriers under the influence of polar solvents. This leads to the paradoxical phenomenon of "stable interface but unstable bulk phase" in existing systems during liquid-phase photocatalytic reactions. Consequently, specific research on their application in the dehydrogenation of ethanol to prepare acetal remains relatively scarce, and in-depth exploration of related mechanisms and process optimization is still needed. Summary of the Invention

[0004] To address the limitations of traditional photocatalysts, such as narrow light absorption range, high charge recombination rate, and insufficient stability, which hinder efficient photocatalytic reactions, this invention discloses a perovskite composite photocatalyst for photocatalytic ethanol dehydrogenation and its applications. This includes the development of a novel composite photocatalyst that combines the excellent light absorption characteristics of Cs₂AgBiBr₆ with the high conduction band position advantage of CdS, aiming to achieve efficient separation and transport of photogenerated electron-hole pairs, thereby improving photocatalytic efficiency. The selectivity of the liquid-phase products is controlled through metal loading.

[0005] To achieve the above objectives, the present invention includes the following technical solutions:

[0006] A perovskite composite photocatalyst for photocatalytic ethanol dehydrogenation, the composite photocatalyst comprising CdS nanorods and an active component supported on the surface of the CdS nanorods;

[0007] The active component is Cs2AgBiBr6.

[0008] Furthermore, in the aforementioned composite photocatalyst, the active component Cs₂AgBiBr₆ supported on the surface of CdS nanorods is formed from precursors CsBr, AgBr, and BiBr₃ via a vacuum in-situ growth method. Preferably, the molar ratio of CsBr, AgBr, and BiBr₃ is 2:1:1.

[0009] Furthermore, in the above-mentioned composite photocatalyst, the loading of Cs2AgBiBr6 is 5% to 15% of the mass of CdS nanorods.

[0010] Furthermore, the aforementioned composite photocatalyst also supports a metal co-catalyst, which is selected from Pt, Rh, and Ni; the loading amount of the metal co-catalyst, based on the mass of the metal element, is 2% to 5% of the total mass of the composite photocatalyst.

[0011] This invention also discloses a method for preparing the above-mentioned composite photocatalyst, comprising the following steps:

[0012] (a) Providing CdS nanorods and metal halide precursors;

[0013] (b) The CdS nanorods and the precursor are dispersed in a mixed organic solvent composed of dichloromethane and toluene, and ultrasonically treated for more than 10 minutes to form a uniform suspension;

[0014] (c) Place the suspension in a Schlenk tube and perform a cycle of liquid nitrogen freezing-vacuum evacuation-room temperature dissolution at least twice using a double-row tube system, and then stir under vacuum or inert atmosphere for 20 to 30 min.

[0015] (d) The system treated in step (c) is heated in an oil bath at 100 °C to 110 °C and all organic solvents are removed under vacuum to obtain the composite photocatalyst.

[0016] Furthermore, the above preparation method further includes step (e) after step (d): collecting the obtained composite photocatalyst by centrifugation, washing it with diethyl ether, and then drying it under vacuum at 60 °C.

[0017] Furthermore, in the above preparation method, when a metal co-catalyst is supported, the following photodeposition step is also included after step (d):

[0018] 1) Disperse the composite photocatalyst obtained in step (d) in ethanol;

[0019] 2) Add an ethanol solution containing the metal cocatalyst precursor, wherein the metal cocatalyst precursor is chloroplatinic acid hexahydrate, rhodium chloride trihydrate, or nickel chloride hexahydrate;

[0020] 3) Perform the liquid nitrogen freezing-vacuum evacuation-room temperature dissolution cycle on the mixed system at least twice;

[0021] 4) Irradiate with a light source with a wavelength greater than 420 nm for 1 to 2 hours in an inert atmosphere;

[0022] 5) Centrifuge to collect the product and dry it to obtain a composite photocatalyst supported on a metal co-catalyst.

[0023] This invention also discloses a method for photocatalytic dehydrogenation of ethanol to prepare acetaldehyde, acetal, and hydrogen, comprising at least the following steps:

[0024] Ethanol was brought into contact with a composite photocatalyst and reacted under anaerobic conditions and light irradiation.

[0025] Furthermore, in the above method, the illumination is visible light with a wavelength greater than or equal to 420 nm and an illumination intensity of 100 mW / cm². 2 Up to 400 mW / cm 2 The reaction is carried out at room temperature for a period of 1 hour to 60 hours.

[0026] The present invention also discloses the application of the above-mentioned composite photocatalyst in photocatalytic hydrogen production or photocatalytic alcohol dehydrogenation reaction.

[0027] Compared with the prior art, the present invention has the following outstanding advantages:

[0028] 1. By carefully designing the Rh-Cs2AgBiBr6 / CdS composite photocatalyst and controlling material factors and reaction parameters such as the composition ratio of the heterojunction material, the type and loading of the metal co-catalyst, the amount of photocatalyst used, the incident light wavelength range and irradiation intensity, and the photoreaction time, we obtained an Rh-Cs2AgBiBr6 / CdS photocatalyst with excellent photocatalytic ethanol dehydrogenation performance. The optimized direct ethanol dehydrogenation performance reached 49.2 mmol g. -1 h -1 The apparent quantum efficiency of hydrogen production is as high as 22.5%, and the catalyst exhibits long-term reaction stability.

[0029] 2. This invention fully utilizes the synergistic catalytic effect among halide perovskites, semiconductor materials, and noble metals. The synergistic effect of the Cs₂AgBiBr₆ / CdS heterojunction and the Rh metal co-catalyst effectively regulates the selective distribution of the liquid-phase organic products acetaldehyde and acetal, with the loading of the metal co-catalyst promoting the formation of acetaldehyde. This unique combination not only enhances the absorption and conversion of light energy but also promotes the effective separation of photogenerated electrons and holes, thereby significantly improving the catalytic efficiency of the ethanol dehydrogenation reaction and resulting in a significant increase in the yield of acetal.

[0030] 3. Halide perovskite materials themselves possess excellent chemical stability, and the combination with CdS and Rh further enhances the catalyst's stability and resistance to photocorrosion. This means that the catalyst can maintain high catalytic activity even under prolonged light and reaction conditions, extending its lifespan and reducing production costs.

[0031] 4. This invention not only expands the types of heterojunction photocatalysts based on lead-free halide perovskites, but also extends halide perovskite photocatalysts from most traditional nonpolar or low-polar organic solvent reaction systems to organic polar solvent systems, providing a new method for designing and constructing halide perovskite photocatalytic hydrogen production systems with high activity, high selectivity and high stability. Attached Figure Description

[0032] Figure 1 The characterization results of Cs2AgBiBr6 powder in ethanol before and after phototreatment under different atmospheres (Ar / Air) are as follows: (a) XRD pattern, (b) UV-Vis diffuse reflectance absorption spectrum.

[0033] Figure 2 XPS spectra of Cs2AgBiBr6 powder before and after phototreatment in ethanol under different atmospheres (Ar / Air): (a) full spectrum, (c) Cs 3d, (d) Ag 3d, (e) Bi 4f and (f) Br 3d;

[0034] Figure 3 The images show the XRD patterns of Cs2AgBiBr6, CdS, and CdS with different amounts of Cs2AgBiBr6 in this invention.

[0035] Figure 4 SEM images of Cs2AgBiBr6 powder before and after photo-treatment in ethanol under different atmospheres (Ar / Air) according to the present invention: (a) Dark, (b) Ar atmosphere, after 4 h of reaction under visible light, (c) Air atmosphere, after 4 h of photo-reaction under visible light.

[0036] Figure 5The images show SEM images of Cs2AgBiBr6, CdS, and Cs2AgBiBr6 / CdS from the present invention (ac);

[0037] Figure 6 The figures are (a) a blank experimental performance diagram of photocatalytic alcohol dehydrogenation of the present invention, and (b) a photocatalytic alcohol dehydrogenation rate diagram of CdS-supported precursors.

[0038] Figure 7 The graph shows the photocatalytic hydrogen production rate of ethanol using Cs2AgBiBr6 / CdS with different Cs2AgBiBr6 loadings according to the present invention.

[0039] Figure 8 This figure shows the effect of different metal co-catalysts on the photocatalytic ethanol dehydrogenation rate of Cs2AgBiBr6 / CdS according to the present invention.

[0040] Figure 9 The graph shows the photocatalytic ethanol dehydrogenation performance of Rh-Cs2AgBiBr6 / CdS with different Rh loadings according to the present invention.

[0041] Figure 10 The photocatalytic ethanol dehydrogenation performance of different photocatalysts under full-spectrum and visible light conditions (λ > 420 nm) is shown in the figure: (a) photocatalytic ethanol dehydrogenation rate diagram, (b) photocatalytic ethanol dehydrogenation molar amount diagram.

[0042] Figure 11 The graph shows the formation rate of photocatalytic ethanol dehydrogenation products of CdS, Cs3Sb2Br9 / CdS, Cs3Bi2Br9 / CdS, Cs2AgBiBr6 / CdS, Rh-CdS and Rh-Cs2AgBiBr6 / CdS of the present invention.

[0043] Figure 12 Selective distribution of liquid-phase products in the photocatalytic ethanol dehydrogenation reaction of the Rh-CdS, Cs2AgBiBr6 / CdS and Rh-Cs2AgBiBr6 / CdS photocatalysts of the present invention;

[0044] Figure 13 The following are gas chromatograms of (a) the standard acetaldehyde, (b) the standard acetal, and (c) the product of the Rh-Cs2AgBiBr6 / CdS photocatalytic ethanol dehydrogenation reaction.

[0045] Figure 14 The photocatalytic ethanol dehydrogenation performance (AQY) and the UV-Vis absorption spectra of the photocatalyst under different wavelength conditions of the present invention are shown.

[0046] Figure 15The XRD patterns of the Rh-Cs2AgBiBr6 / CdS photocatalyst before and after the ethanol dehydrogenation reaction of the present invention are shown below.

[0047] Figure 16 The reaction stability evaluation of the Rh-Cs2AgBiBr6 / CdS photocatalytic ethanol dehydrogenation of the present invention is as follows: (a) long-term reaction performance diagram, (b) cyclic reaction performance diagram. Within the initial 10 h of the reaction, the photocatalytic hydrogen production activity gradually increases;

[0048] Figure 17 The images show the SEM spectra of the Rh-Cs2AgBiBr6 / CdS photocatalysis of the present invention before (a) and after (b) the reaction.

[0049] Figure 18 Detection of reaction intermediates using Rh-Cs2AgBiBr6 / CdS as a photocatalyst: (a) Photocatalytic alcohol dehydrogenation performance in the presence of different trapping agents, (b) In-situ EPR diagram. Detailed Implementation

[0050] Compared to typical ABX3 perovskites, the A-site in a double perovskite structure is typically occupied by a larger radius cation (such as Cs). + The presence of B-sites helps stabilize its cubic crystal structure. The B-sites, formed by alternating heterovalent metal cations in an ordered manner to create an octahedral, interconnected, three-dimensional rigid framework, significantly enhance lattice stability, giving it a significant advantage in photocatalysis. Firstly, this material exhibits high intrinsic chemical stability, maintaining stable performance in polar organic solvents such as ethanol, thus avoiding the deactivation problem of traditional photocatalytic materials in organic solvents. CdS possesses a suitable band gap (2.4 eV) and visible light response, making it well-suited for photocatalytic applications. Furthermore, its redox potential covers almost all redox reactions of organic compounds, making it an ideal material for the widespread application of photocatalytic organic degradation and synthesis. Metal co-catalysts play a crucial role in regulating the photocatalytic hydrogen production activity of alcohols. Therefore, constructing heterojunctions and loading metal particles holds promise for achieving highly efficient photocatalytic ethanol dehydrogenation based on halide perovskites.

[0051] This invention leverages the photostability of Cs₂AgBiBr₆ halide perovskite in the polar solvent of ethanol to construct a heterojunction photocatalyst based on CdS and Cs₂AgBiBr₆, successfully applying it to the activation of α-CH / OH bonds and direct dehydrogenation of ethanol. Experimental results show that this heterostructure significantly improves the reaction efficiency of ethanol dehydrogenation to acetal. Further loading with metal co-catalysts Pt, Ni, and Rh further enhances the catalytic performance, with the Rh-based co-catalyst exhibiting the best activity. Under optimal Rh loading and photoconditioning, the photocatalytic hydrogen production rate of Rh-Cs₂AgBiBr₆ / CdS reaches 49.15 mmol g. -1 h -1 The efficiency was improved by 2.11 times compared to the unmodified sample, with an apparent quantum efficiency of 22.5%. Furthermore, the catalyst maintained high catalytic activity and stability after 60 h of continuous reaction, demonstrating good potential for industrial application. Mechanistic studies showed that the construction of the Cs2AgBiBr6 / CdS heterostructure and the loading of the Rh metal co-catalyst synergistically regulated the activity of photocatalytic ethanol dehydrogenation and the selectivity of the organic products acetaldehyde and acetal, providing a new strategy for the high-value conversion of ethanol through photocatalysis.

[0052] This invention utilizes Cs₂AgBiBr₆ and CdS to construct a heterojunction photocatalyst. Through a carefully designed synthetic route, uniform and compact loading of Cs₂AgBiBr₆ nanoparticles onto the surface of CdS nanorods was achieved. This heterojunction structure not only expands the light absorption range but also promotes the spatial separation of photogenerated electron-hole pairs, reducing recombination losses. In particular, when the loading of Cs₂AgBiBr₆ was optimized to 15 wt%, the characteristic peaks of Cs₂AgBiBr₆ were clearly displayed in the XRD pattern, demonstrating the successful formation of the heterojunction and its good crystallinity.

[0053] (1) Synthesis of CdS nanorods: CdCl2·2.5H2O and CH4N2S were completely dissolved in ethylenediamine using an optimized hydrothermal method. The mixture was then transferred to a hydrothermal reactor lined with polytetrafluoroethylene. By precisely controlling the reaction temperature and time, the high-quality synthesis of CdS nanorods was ensured. After cooling to room temperature, the nanorods were washed several times with deionized water and ethanol, providing an ideal substrate for the subsequent construction of heterostructures.

[0054] (2) Preparation of Cs2AgBiBr6 nanoparticles:

[0055] 1. Raw material preparation and mixing: Accurately weigh the perovskite precursors CsBr, AgBr, and BiBr3, and then add these raw materials to a 48% (w / w) HBr aqueous solution. This step ensures the accurate proportion of raw materials, laying a good foundation for subsequent reactions.

[0056] 2. Heating and Dissolving: The mixture is heated to a suitable temperature and maintained at that temperature for several hours to promote the complete dissolution and initial reaction of the raw materials. This stage promotes the interaction between ions through high temperature, creating conditions for the formation of the Cs₂AgBiBr₆ crystal structure.

[0057] 3. Cooling Crystallization and Precipitation: Subsequently, the reaction system was naturally cooled to room temperature and allowed to stand for a period of time to promote the precipitation of Cs2AgBiBr6 nanoparticles. At this time, the formation of orange powder can be observed, marking the initial formation of nanoparticles.

[0058] 4. Preliminary purification: The precipitate was collected by centrifugation and washed three times with diethyl ether to remove impurities adhering to the surface of the nanoparticles. This step effectively improved the purity of the product.

[0059] 5. Fine Purification: To further improve the quality of the nanoparticles, the preliminarily purified crude Cs2AgBiBr6 product was dissolved in a certain amount of DMSO to form a transparent solution. This solution was then slowly added dropwise to a certain amount of dichloromethane (DCM) antisolvent to induce the re-precipitation of the nanoparticles. Fine purification of the nanoparticles was achieved through three repeated processes of centrifugation, precipitation, and ether washing.

[0060] 6. Drying and Storage: Finally, the purified Cs2AgBiBr6 nanoparticles were placed in a vacuum drying oven and dried overnight to ensure complete removal of residual solvent. The dried nanoparticles should be stored away from light to prevent photolysis or performance degradation.

[0061] (3) Furthermore, a unique vacuum in-situ growth method is employed to induce strong interactions between Cs2AgBiBr6 nanoparticles and the surface of CdS nanorods under vacuum conditions, forming a tight heterojunction interface. This method not only simplifies the preparation process but also significantly improves the quality and stability of the heterojunction.

[0062] 1. Raw material preparation: First, high-quality CdS nanorods were selected as the substrate material to ensure good crystallinity and uniform morphology. Simultaneously, different amounts of Cs₂AgBiBr₆ nanoparticles were prepared as key components to enhance photocatalytic activity, in order to explore the optimal loading conditions.

[0063] 2. Dispersion and Mixing: The CdS nanorods prepared in (1) and the Cs2AgBiBr6 nanoparticles prepared in (2) were dispersed in Schlenk tubes containing a certain amount of DCM and toluene, respectively. Ultrasonic treatment was used to ensure uniform dispersion of the nanoparticles in the solvent, forming a stable suspension. Subsequently, the two suspensions were carefully mixed, and mechanical stirring was used to further promote uniform mixing.

[0064] 3. Vacuum Treatment and Solvent Removal: To enhance the interaction between Cs₂AgBiBr₆ nanoparticles and CdS nanorods, a dual-row tube system was used for two cycles of liquid nitrogen freezing-vacuum evacuation-room-temperature dissolution (freeze-evacuate-dissolve). This process effectively removed dissolved gases and impurities from the solution, while promoting the adsorption and rearrangement of nanoparticles on the CdS surface. Subsequently, the mixture was continuously stirred under vacuum for 20-30 min to ensure sufficient contact between the two materials and the formation of a stable heterostructure.

[0065] 4. Solvent Evaporation and Product Collection: Using a double-row vacuum system, the organic solvent in the Schlenk tube was slowly evaporated under oil bath heating conditions of 100 °C - 110 °C. This step requires strict control of the heating rate and vacuum level to avoid damaging the nanostructure. After complete solvent evaporation, the Cs2AgBiBr6 / CdS heterojunction composite material was prepared.

[0066] (4) Post-processing and storage: The obtained composite material was collected by centrifugation and washed three times with diethyl ether to remove residual solvent and impurities. Subsequently, it was dried overnight in a vacuum drying oven at 60 °C to ensure that the product was completely dry and all volatile components were removed. The final Cs2AgBiBr6 / CdS heterojunction material should be stored away from light to prevent unnecessary reactions of the photosensitive components.

[0067] (5) Furthermore, by doping the Cs2AgBiBr6 / CdS composite photocatalyst with the optimal Cs2AgBiBr6 loading for photocatalytic ethanol dehydrogenation, noble metals Rh, Pt, and Ni were obtained, resulting in Cs2AgBiBr6 / CdS catalysts with different metal loadings. Rh doping can optimize the photoelectric properties and catalytic activity of the catalyst, thereby improving the efficiency and selectivity of the ethanol dehydrogenation reaction.

[0068] (6) Photocatalysts such as BiBr3 / CdS, CsBr / CdS, AgBr / CdS, Bi2S3 / CdS and AgS / CdS also adopt a unique vacuum in-situ growth method. Other methods are as above (1)-(4).

[0069] (7) Photocatalytic ethanol dehydrogenation reaction:

[0070] Furthermore, under illumination, ethanol and the composite photocatalyst prepared above are placed in the reaction system to carry out the ethanol dehydrogenation reaction. The illumination conditions can be simulated sunlight or a light source of a specific wavelength, such as an LED lamp or a xenon lamp.

[0071] Furthermore, by adjusting parameters such as light intensity, reaction temperature, reaction time, and catalyst dosage, the reaction conditions were optimized to improve the efficiency of ethanol dehydrogenation and the yield of liquid-phase products. Gas-phase products were detected using gas chromatography and quantitatively analyzed using the external standard method, while small organic molecule products were qualitatively and quantitatively analyzed using gas chromatography-mass spectrometry.

[0072] (8) Finally, the mechanism study was verified through photocatalytic sacrificial agent experiments:

[0073] By introducing free radical or photogenerated electron / hole scavengers (2,2,6,6-tetramethylpiperidine oxide (TEMPO), potassium iodide (KI), carbon tetrachloride (CCl4), 5,5-dimethyl-1-pyrrolline-N-oxide (DMPO), and butylated hydroxytoluene (BHT)), the active substances and intermediates in the photocatalytic process were investigated in depth, revealing the mechanism of the photocatalytic reaction. This research not only provides theoretical guidance for optimizing photocatalysts but also opens up possibilities for expanding their application scope.

[0074] Furthermore, as described in (1), the reaction temperature and reaction time are 150 ℃-160 ℃ and 50 h-60 h, respectively, to ensure the uniform generation of CdS nanorods.

[0075] Furthermore, in (2), the molar ratio of the perovskite precursors CsBr, AgBr and BiBr3 must be maintained at 2:1:1.

[0076] Furthermore, in (2), the precursor mixture is stored at 100 ℃-110 ℃ for 1-2 h to ensure that the precursor is completely dissolved.

[0077] Furthermore, as mentioned in (3), the loading of Cs2AgBiBr6 is set to 0%-15%. Excessive loading will mask the reactive sites and reduce the photocatalytic reaction performance.

[0078] Furthermore, the oil bath temperature described in (3) is maintained at 100 ℃-110 ℃ to ensure that the solvent can evaporate as much as possible.

[0079] Furthermore, for the Cs2AgBiBr6 / CdS catalysts with different metal loadings described in (4), it is better to have a metal loading range of 2%-5%. Too much metal loading will mask the reactive sites of the catalyst and reduce the performance of photocatalytic ethanol dehydrogenation.

[0080] Furthermore, the ethanol solution described in (4) containing different metals, namely chloroplatinic acid hexahydrate, rhodium chloride trihydrate and nickel chloride hexahydrate, has a concentration of 100 mg / mL.

[0081] Furthermore, the different wavelengths of monochromatic light from LED lamps described in (5) were used as light sources at 420 nm, 470 nm, 520 nm and 620 nm to determine the performance of ethanol dehydrogenation and the apparent quantum efficiency of hydrogen production.

[0082] Furthermore, the light intensity mentioned in (5) is 100 mW / cm². 2 -400 mW / cm 2 The reaction temperature was optimized to room temperature, the reaction time to be 1 h–60 h, and the amount of catalyst to be 1 mg–5 mg. Furthermore, the reaction was carried out under anaerobic conditions and with the full spectrum of light to produce hydrogen.

[0083] Furthermore, the amount of the precursors BiBr3, CsBr, AgBr, Bi2S3 and AgS introduced in (6) is 10%.

[0084] Furthermore, the amount of the scavenger that introduces free radicals or photogenerated electrons / holes as described in (7) is 10 μL or 5 mg.

[0085] The produced hydrogen gas was tested and found to contain no carbon dioxide.

[0086] The Cs₂AgBiBr₆ / CdS catalyst prepared using the method of this invention exhibits better ethanol dehydrogenation performance compared to other catalysts. Furthermore, it is CO-free. x The process does not require stringent conditions of high temperature and high pressure, thus saving resources. The catalyst has stable performance and can continuously produce hydrogen, formaldehyde, and acetal, providing valuable reference for the industrial production of formaldehyde.

[0087] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0088] Example 1: Preparation of CdS nanorods.

[0089] CdS nanorods were synthesized via a hydrothermal method. First, 20.2 mmol (4.62 g) of CdCl₂·2.5H₂O and 60.7 mmol (4.62 g) of CH₄N₂S were completely dissolved in 60 mL of ethylenediamine, and then transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene. The reactor was then placed in a forced-air drying oven at 5°C. o C min -1The temperature was increased from room temperature to 160℃ at a controlled heating rate and held for 50 h. After natural cooling to room temperature, the sample was centrifuged, washed three times with ultrapure water and three times with anhydrous ethanol. It was then vacuum-dried at 60℃ for 12 h and stored away from light.

[0090] Example 2: Preparation of Cs2AgBiBr6 nanoparticles.

[0091] Cs₂AgBiBr₆ nanoparticles were synthesized via a cooling crystallization method. 0.426 g CsBr (2.0 mmol), 0.188 g AgBr (1.0 mmol), and 0.449 g BiBr₃ (1.0 mmol) were added to 10 mL of a 48% (w / w) HBr aqueous solution. The mixture was heated to 110°C. o The product was kept at C for 2 h, then cooled to room temperature. After standing to precipitate, an orange powder formed. The crude product was then collected by centrifugation at 6000 rpm for 2 min and washed three times with diethyl ether. Subsequently, it was... o The crude Cs₂AgBiBr₆ product was dried overnight in a vacuum oven at C. 50 mg of the crude Cs₂AgBiBr₆ product was dissolved in 2 mL of DMSO to obtain a clear solution. Then, 1 mL of the Cs₂AgBiBr₆ / DMSO clear solution was added to 30 mL of DCM antisolvent, followed by centrifugation, precipitation, and washing with ether three times. Finally, the product was dried at 60 °C. o Cs2AgBiBr6 nanoparticles were obtained by vacuum drying under reduced pressure overnight and stored away from light.

[0092] Example 3: Preparation of Cs2AgBiBr6 / CdS heterojunction.

[0093] First, 100 mg of CdS nanorods (Example 1) and 5 mg of Cs₂AgBiBr₆ nanoparticles (Example 2) were dispersed in Schlenk tubes containing 20 mL of DCM and 2 mL of toluene, respectively, and then sonicated for 10 min to achieve uniform dispersion. The solutions were then thoroughly mixed and subjected to a double-row tube system of liquid nitrogen freezing-vacuum evacuation-room-temperature dissolution (freeze-evacuation-dissolve), repeated twice, with stirring under vacuum for 20 min. Finally, a double-row tube vacuum system was used to dissolve the nanoparticles at 110°C. o The organic solvent in the vacuum glass tube was removed by heating in an oil bath (C) to obtain the Cs₂AgBiBr₆ / CdS heterojunction. The product was then collected by centrifugation at 6000 rpm for 2 min and washed three times with diethyl ether. [Further details about the product and its properties are needed for accurate translation.] o Vacuum drying at C20°C overnight yields Cs2AgBiBr6 / CdS heterojunction material, which is then stored in the dark for later use.

[0094] Example 4: Preparation of Cs2AgBiBr6 / CdS heterojunction.

[0095] 100 mg of CdS nanorods (Example 1) and 10 mg of Cs₂AgBiBr₆ nanoparticles (Example 2) were dispersed in Schlenk tubes containing 20 mL of DCM and 2 mL of toluene, respectively, and then sonicated for 10 min to achieve uniform dispersion. The solutions were then mixed thoroughly and subjected to a double-row tube system of liquid nitrogen freezing-vacuum evacuation-room-temperature dissolution (freeze-evacuation-dissolve), repeated twice, with stirring under vacuum for 20 min. Finally, a double-row tube vacuum system was used to dissolve the nanoparticles at 110°C. o The organic solvent in the vacuum glass tube was removed by heating in an oil bath (C) to obtain the Cs₂AgBiBr₆ / CdS heterojunction. The product was then collected by centrifugation at 6000 rpm for 2 min and washed three times with diethyl ether. [The remaining text appears to be incomplete and requires further context.] o Vacuum drying at C20°C overnight yields Cs2AgBiBr6 / CdS heterojunction material, which is then stored in the dark for later use.

[0096] Example 5: Preparation of Cs2AgBiBr6 / CdS heterojunction.

[0097] 100 mg of CdS nanorods (Example 1) and 15 mg of Cs₂AgBiBr₆ nanoparticles (Example 2) were dispersed in Schlenk tubes containing 20 mL of DCM and 2 mL of toluene, respectively, and then sonicated for 10 min to achieve uniform dispersion. The solutions were then mixed thoroughly and subjected to a liquid nitrogen freezing-vacuum evacuation-room-temperature dissolution (freeze-evacuation-dissolve) process using a double-row vacuum system, repeated twice, with stirring under vacuum for 20 min. Finally, the mixture was dissolved at 110 °C using a double-row vacuum system. o The organic solvent in the vacuum glass tube was removed by heating in an oil bath (C) to obtain the Cs₂AgBiBr₆ / CdS heterojunction. The product was then collected by centrifugation at 6000 rpm for 2 min and washed three times with diethyl ether. [Further details about the product and its properties are needed for accurate translation.] o Vacuum drying at C20°C overnight yields Cs2AgBiBr6 / CdS heterojunction material, which is then stored in the dark for later use.

[0098] Example 6: Preparation of Rh-CdS heterojunction.

[0099] The sample from Example 1 was dispersed in a Schlenk tube containing 5 mL of ethanol and then sonicated for 10 min to achieve uniform dispersion. Next, 40 μL of an ethanol solution of rhodium chloride trihydrate was added. A double-row tube was used for liquid nitrogen freezing-vacuum evacuation-room-temperature dissolution (freeze-evacuate-dissolve) treatment, repeated twice, followed by stirring under Ar conditions for 5 min. Subsequently, a 300 W xenon lamp (λ > 420 nm) was used as the light source for the photocatalytic reaction, and the suspension was irradiated for 1.5 h. After centrifugation for 5 min, 2 mL of ethanol was added for washing, and then the mixture was centrifuged at 60 °C. o The Rh-CdS photocatalyst was obtained by drying in a vacuum drying oven overnight.

[0100] Example 7: Preparation of Rh-Cs2AgBiBr6 / CdS photocatalyst.

[0101] The sample from Example 4 was dispersed in a Schlenk tube containing 5 mL of ethanol and then sonicated for 10 min to achieve uniform dispersion. Next, 40 μL of an ethanol solution of rhodium chloride trihydrate was added. A double-row tube was used for liquid nitrogen freezing-vacuum evacuation-room-temperature dissolution (freeze-evacuate-dissolve) treatment, repeated twice, followed by stirring under Ar conditions for 5 min. Subsequently, a 300 W xenon lamp (λ > 420 nm) was used as the light source for the photocatalytic reaction, and the suspension was irradiated for 1.5 h. After centrifugation for 5 min, 2 mL of ethanol was added for washing, and then the mixture was dried overnight in a vacuum drying oven at 60 ℃ to obtain the 4% Rh-Cs2AgBiBr6 / CdS photocatalyst.

[0102] Example 8: Preparation of Pt-Cs2AgBiBr6 / CdS photocatalyst.

[0103] The sample from Example 4 was dispersed in a Schlenk tube containing 5 mL of ethanol and then sonicated for 10 min to achieve uniform dispersion. Next, 40 μL of an ethanol solution of chloroplatinic acid hexahydrate was added. A double-row tube was used for liquid nitrogen freezing-vacuum evacuation-room-temperature dissolution (freeze-evacuate-dissolve) treatment, repeated twice, followed by stirring under Ar conditions for 5 min. Subsequently, a 300 W xenon lamp (λ > 420 nm) was used as the light source for the photocatalytic reaction, and the suspension was irradiated for 1.5 h. After centrifugation for 5 min, 2 mL of ethanol was added for washing, and then the mixture was dried overnight in a vacuum drying oven at 60 ℃ to obtain the 4% Pt-Cs2AgBiBr6 / CdS photocatalyst.

[0104] Example 9: Preparation of Ni-Cs2AgBiBr6 / CdS photocatalyst.

[0105] The sample from Example 4 was dispersed in a Schlenk tube containing 5 mL of ethanol and then sonicated for 10 min to achieve uniform dispersion. Next, 40 μL of an ethanol solution of nickel chloride hexahydrate was added. A double-row tube was used for liquid nitrogen freezing-vacuum evacuation-room-temperature dissolution (freeze-evacuate-dissolve) treatment, repeated twice, followed by stirring under Ar conditions for 5 min. Subsequently, a 300 W xenon lamp (λ > 420 nm) was used as the light source for the photocatalytic reaction, and the suspension was irradiated for 1.5 h. Afterwards, the ethanol solvent was removed using a double-row tube to obtain the 4% Ni-Cs2AgBiBr6 / CdS photocatalyst.

[0106] Test Example 1: XRD structural characterization of the catalyst.

[0107] To thoroughly evaluate the structural stability and integrity of Cs2AgBiBr6 before and after phototreatment under different atmospheric conditions (inert atmosphere Ar, oxidizing atmosphere Air), this invention conducted a systematic comparative analysis. XRD results ( Figure 1 a) shows that the peak positions and shapes of the characteristic diffraction peaks of Cs₂AgBiBr₆ powder did not shift significantly after different atmospheric illumination treatments. This indicates that the crystal structure of Cs₂AgBiBr₆ remained highly stable under the experimental conditions and was not affected by the type of atmosphere or illumination treatment. UV-Vis DRS characterization ( Figure 1 (b) shows that the light absorption capacity and absorption edge of Cs2AgBiBr6 powder did not change significantly before and after treatment with different atmospheres and light environments. This indicates that the material maintains good optical property stability in ethanol solvent system and under different atmospheres and light environments.

[0108] Test Example 2: Surface Chemical State Analysis (XPS).

[0109] via XPS ( Figure 2 Analysis of key elements (Cs 3d, Ag 3d, Bi 4f, Br 3d) on the material surface revealed that the characteristic binding energy peak positions and relative peak intensities of each element remained consistent before and after treatment, with no significant chemical shifts or intensity changes. Crucially, no elements corresponding to metallic elements (such as Ag) were detected. 0 Bi 0 The characteristic signals of newly formed halide species (such as AgBr, BiBr3, etc.) are also present. This proves that the elemental composition and chemical state of the material surface did not change under different atmospheric illumination conditions.

[0110] Test Example 3: Characterization of catalytic performance with different Cs2AgBiBr6 loadings.

[0111] Cs2AgBiBr6 / CdS composite photocatalysts with different Cs2AgBiBr6 loadings (5-15 wt%) were characterized by XRD. Figure 3 When the loading was ≤10 wt%, no characteristic peaks of Cs2AgBiBr6 were detected due to the low loading of Cs2AgBiBr6. When the loading was increased to 15 wt%, characteristic diffraction peaks of Cs2AgBiBr6 were observed at 2θ=22.37°, 31.74°, 39.26° and 45.65°, which were attributed to the (022), (004), (224) and (044) crystal planes of cubic perovskite, respectively, further confirming that Cs2AgBiBr6 had been successfully loaded onto CdS. In addition, the positions and intensities of the characteristic diffraction peaks of CdS remained stable in all samples, indicating that the recombination process did not change the crystal structure of CdS.

[0112] Test Example 4: SEM characterization of microstructure before and after illumination under different atmospheres.

[0113] This invention employs an anti-solvent precipitation method to prepare Cs2AgBiBr6 nanoparticles (their morphology characteristics are as follows). Figure 4 (as shown in a). Subsequently, the nanoparticles were combined with CdS nanorods (morphology as shown in a) pre-synthesized via a hydrothermal method. Figure 4 As shown in b), a Cs2AgBiBr6 / CdS heterojunction composite material was successfully constructed using an in-situ growth strategy (composite structure as shown in b). Figure 4 (as shown in c).

[0114] Test Example 5: SEM characterization of catalyst microstructure.

[0115] This invention uses scanning electron microscopy (SEM) to systematically characterize the morphology of Cs2AgBiBr6, CdS, and Cs2AgBiBr6 / CdS composite materials. For example... Figure 5 As shown in figure a, Cs₂AgBiBr₆ mainly exists in the form of nanoparticles, with a particle size distribution in the range of 200-500 nm, and the overall size is relatively uniform; from Figure 5 As can be seen from b, CdS mainly consists of nanorod-like structures with lengths between 1 and 2 μm. SEM images of the Cs₂AgBiBr₆ / CdS heterojunction composite material prepared by the in-situ composite method are shown in [image / image / details]. Figure 5 c. It can be clearly observed that Cs2AgBiBr6 nanoparticles are uniformly distributed on the surface of CdS nanorods. This morphological feature effectively confirms the successful construction of Cs2AgBiBr6 / CdS heterostructure.

[0116] Test Example 6: The effect of precursors on photocatalytic activity.

[0117] To systematically evaluate the intrinsic photocatalytic activity of the photocatalyst for ethanol dehydrogenation, this invention was conducted under standard reaction conditions (2 mg catalyst, 5 mL ethanol, Ar atmosphere, λ > 420 nm, light intensity: 300 mW cm⁻¹). -2 A series of controlled experiments were conducted. For example... Figure 6 As shown in Figure a, no H2 generation was detected in either the blank experimental group (without catalyst) or the dark reaction group, indicating that the reaction strictly depends on photoexcitation. Notably, no hydrogen production activity was observed in the supernatant obtained after centrifugation of the reaction solution after stirring for 2 hours, effectively ruling out the contribution of homogeneous reaction or metal ion dissolution to the catalytic system. To further explore the synergistic effect of each component in the composite catalyst, the present invention also designed and prepared the following comparative samples: single precursors (CsBr, BiBr3, SbBr3) supported on CdS, and binary composite structures of Ag2S / CdS and Bi2S3 / CdS possibly generated by interfacial reactions. Figure 6 As shown in b, the precursor-supported system exhibited only trace hydrogen production activity (<0.8 mmol g). -1 h -1 The concentration was significantly lower than that of the Cs2AgBiBr6 / CdS composite system (8.25 mmol g). -1 h -1 Similarly, the hydrogen production rates of Ag₂S / CdS and Bi₂S₃ / CdS were also low, at 1.25 and 1.07 mmol g, respectively. -1 h -1 This further illustrates that the interfacial coupling between Cs2AgBiBr6 and CdS plays a key role in improving photocatalytic performance.

[0118] Test Example 7: Effect of Cs2AgBiBr6 loading on hydrogen production performance.

[0119] 5 mg of photocatalyst (samples from Examples 3-5) was weighed and dispersed in 5 mL of ethanol, then added to a 62 mL Schlenk glass reaction tube. Oxygen was effectively removed from the reaction system through repeated cycles of liquid nitrogen freezing, vacuum evacuation, and room temperature dissolution (freeze-evacuate-dissolve), followed by purging with argon as an inert atmosphere. Subsequently, a 300 W xenon lamp (λ > 420 nm) was used as the light source for the photocatalytic reaction, irradiating the suspension for a certain period (4 h). Hydrogen products were detected by gas chromatography. Figure 7 As shown, the photocatalytic hydrogen production rate first increases and then decreases with increasing Cs₂AgBiBr₆ loading. The performance is optimal when the loading is 10 wt%, with a hydrogen production rate reaching 8.25 mmol g⁻¹. -1 h -1The performance degradation is likely mainly attributed to factors such as the shielding effect of excess Cs₂AgBiBr₆ on CdS light absorption, the covering of active sites, and the introduction of additional photogenerated carrier recombination centers. Notably, under the same reaction conditions, pure-phase Cs₂AgBiBr₆ (100 wt%) showed no significant ethanol dehydrogenation activity, indicating that its own photogenerated carriers are insufficient to drive the reaction. However, the photocatalytic performance of ethanol dehydrogenation was significantly improved after recombination with CdS, confirming the synergistic effect between CdS as the main light absorber and Cs₂AgBiBr₆ as the key active site.

[0120] Test Example 8: The effect of different co-catalysts on the photocatalytic ethanol dehydrogenation performance.

[0121] To improve the photocatalytic hydrogen evolution performance of the Cs2AgBiBr6 / CdS heterojunction (10 wt%), this invention employs photodeposition to introduce 2 wt% noble metals (Pt, Rh, Ni) as co-catalysts for interface modification. 5 mg of photocatalyst (samples from Examples 7-9) was weighed and dispersed in 5 mL of ethanol, then added to a 62 mL Schlenk glass reaction tube. Oxygen in the reaction system was effectively removed through repeated cycles of liquid nitrogen freezing-vacuum evacuation-room-temperature dissolution (freeze-evacuate-dissolve), followed by argon purging as an inert atmosphere. Subsequently, a 300 W xenon lamp (λ > 420 nm) was used as the light source for the photocatalytic reaction, irradiating the suspension for a certain period (4 h). Hydrogen products were detected by gas chromatography and quantitatively analyzed using the external standard method. Organic small molecule products were qualitatively and quantitatively analyzed using gas chromatography-mass spectrometry. Experimental results show that the type of co-catalyst has a significant impact on hydrogen evolution activity. Figure 8 Among them, the Rh-modified catalyst exhibited the best activity, with a hydrogen evolution rate of 27.40 mmol g. -1 h -1 Compared with Pt (17.04 mmol g), respectively -1 h -1 ) and Ni (16.37 mmol g -1 h -1 The modified system was 1.61 times and 1.67 times higher.

[0122] Test Example 9: Effect of different Rh loadings on photocatalytic ethanol dehydrogenation performance.

[0123] Photocatalysts with different Rh loadings were weighed and dispersed in 5 mL of ethanol, then added to 62 mL Schlenk glass reaction tubes. Oxygen in the reaction system was effectively removed by repeated cycles of liquid nitrogen freezing, vacuum evacuation, and room temperature dissolution (freezing-evacuation-dissolution), followed by purging with argon as an inert atmosphere. Subsequently, a 300 W xenon lamp (λ > 420 nm) was used as the light source for the photocatalytic reaction, irradiating the suspension for a certain period (4 h). Hydrogen products were detected by gas chromatography. To systematically investigate the structure-activity relationship of Rh loading (0-6 wt%) on the photocatalytic ethanol dehydrogenation performance, this invention conducted optimization experiments. Figure 9 As shown, the ethanol dehydrogenation rate exhibits a volcano-shaped curve distribution with increasing Rh loading, reaching a peak at 4 wt% (49.15 mmol g). -1 h -1 ), compared to the unmodified Cs2AgBiBr6 / CdS sample (8.25 mmol g), -1 h -1 The efficiency was improved by 5.96 times. Mechanism analysis showed that the introduction of an appropriate amount of Rh (4 wt%) can effectively improve the carrier separation efficiency and provide abundant reactive sites through its surface plasmon resonance effect. However, excessive loading (>4 wt%) will induce the light absorption competition effect between the metal-semiconductor interface, reduce the light-harvesting ability of the semiconductor photoactive material, and at the same time, excessive Rh nanoparticles may act as carrier recombination centers, aggravating the nonradiative recombination of photogenerated electron-hole pairs, ultimately causing the catalytic performance to decline.

[0124] Test Example 10: The effect of different light sources on the photocatalytic performance of ethanol dehydrogenation.

[0125] This invention also investigated the ethanol dehydrogenation performance of the Rh-Cs2AgBiBr6 / CdS photocatalyst under different light wavelength ranges. 2 mg of the photocatalyst was weighed and dispersed in 5 mL of ethanol, then added to a 62 mL Schlenk glass reaction tube. Oxygen in the reaction system was effectively removed by repeated cycles of liquid nitrogen freezing-vacuum evacuation-room-temperature dissolution (freezing-evacuation-dissolution), followed by purging with argon as an inert atmosphere. Subsequently, a 300 W xenon lamp (λ > 420 nm) and a full-spectrum Xe lamp (without a λ > 420 nm filter) were used as the light source for the photocatalytic reaction, irradiating the suspension for a certain period (4 h). The hydrogen products were detected by gas chromatography. Figure 10As shown in Figure a, we compared the photocatalytic performance under visible light and full-spectrum conditions. Under both illumination conditions, the photocatalytic alcohol dehydrogenation rate gradually increased with reaction time. Notably, the photocatalytic dehydrogenation rate was significantly higher under full-spectrum conditions than under visible light conditions, indicating that the ultraviolet light band also has a significant promoting effect on the activation of the photocatalyst and the ethanol dehydrogenation reaction. Figure 10 Figure b provides a more intuitive demonstration of the changes in hydrogen production under visible and full-spectrum illumination. The molar amount of photocatalytic hydrogen exhibits a near-linear change with increasing reaction time. The full-spectrum photocatalytic ethanol dehydrogenation yield is higher than that under visible light conditions. This result highlights the importance of the ultraviolet region for the photocatalytic activity in ethanol dehydrogenation.

[0126] Test Example 11: Performance Comparison with Different Photocatalysts.

[0127] In the photocatalytic dehydrogenation of ethanol, different catalysts exhibit significant differences in hydrogen generation performance. Performance comparison results show that ( Figure 11 The Rh-Cs2AgBiBr6 / CdS catalyst exhibited the best catalytic activity, with a hydrogen production rate of 49.15 mmol g. -1 h -1 This study fully demonstrates the crucial role of Rh co-catalysts in enhancing charge separation efficiency and light absorption capacity, thereby significantly improving the photocatalytic performance of Cs2AgBiBr6 / CdS. While Rh-CdS did not reach the high performance of the former, it still exhibited high catalytic activity, indicating that Rh also has a significant catalytic enhancement effect on CdS itself. Although the H2 generation rate of the Cs2AgBiBr6 / CdS composite catalyst was lower than that of similar Rh-modified catalysts, it was superior to Cs3Bi2Br9 / CdS and Cs3Sb2Br9 / CdS, especially the latter, whose extremely low hydrogen generation rate indicates that this type of composite material has weak catalytic activity in this reaction system. From the perspective of the mechanism of action, Rh co-catalysts may significantly improve catalytic performance by providing efficient reaction sites and optimizing electron transport pathways; simultaneously, the heterojunction formed between Cs2AgBiBr6 and CdS may also enhance photocatalytic activity through interfacial charge separation effects. In summary, the Rh-Cs2AgBiBr6 / CdS catalyst exhibits excellent performance in the photocatalytic dehydrogenation of ethanol. This catalyst system not only demonstrates significant innovation and high catalytic efficiency, but also shows clear application potential and high patent protection value in the field of clean energy production.

[0128] Test Example 12: Liquid Phase Product Regulation.

[0129] Figure 12The liquid-phase product distributions of Rh-CdS, Cs₂AgBiBr₆ / CdS heterojunctions, and Rh-Cs₂AgBiBr₆ / CdS in the photocatalytic dehydrogenation of ethanol are presented. The product distribution results indicate that the catalyst structure significantly modulates the reaction pathway and product selectivity. Rh-CdS mainly produces acetaldehyde with a selectivity of 87.2%, while the Cs₂AgBiBr₆ / CdS heterojunction exhibits high selectivity for acetal, reaching 99.1%. Notably, after Rh metal modification of the Cs₂AgBiBr₆ / CdS heterojunction, the product distribution changed significantly, with acetaldehyde and acetal selectivities of 60.2% and 39.8%, respectively. By combining photocatalytic activity and selectivity analysis, this invention reveals the synergistic regulation mechanism between heterostructure construction and noble metal modification: the construction of heterostructure interfaces not only promotes the effective separation of charge carriers and improves hydrogen evolution performance, but also regulates the surface reaction pathway; while the introduction of Rh cocatalyst further optimizes the adsorption behavior of reaction intermediates, thereby achieving precise regulation of CH bond activation and CC coupling processes, and thus achieving precise regulation of product selectivity.

[0130] Test Example 13: Identification of gaseous products.

[0131] Qualitative analysis of photocatalytic organic products was performed by gas chromatography: first, 5 μmol mL solutions were prepared... -1 Acetaldehyde and acetal standard solutions were prepared by taking 1.5 mL of each solution and adding it to a sample vial, and then performing gas chromatography for detection. The test results are as follows: Figure 13 As shown in ab, the gas chromatographic peak of the acetaldehyde standard is at 0.87 min, while the gas chromatographic peak of the acetal standard appears at 1.45 min. From... Figure 13 In the graphs ab and b, it can be observed that although the concentrations of acetaldehyde and acetal are both 5 μmol / mL... -1 However, their signal response in gas chromatography differs; acetaldehyde exhibits a better signal response compared to acetal. Using Rh-Cs2AgBiBr6 / CdS as a photocatalyst, under typical photocatalytic ethanol dehydrogenation reaction conditions (visible light λ > 420 nm, light intensity 100 mW cm⁻¹), -2 The reaction substrate was 5 mL, the reaction atmosphere was Ar, and the photoreaction time was 4 h. The resulting clear solution was filtered through an organic filter membrane. 1.5 mL of this solution was then placed in a sample vial and analyzed using an autosampler and gas chromatography. Figure 13 The gas chromatogram of organic product c clearly shows two peaks at 0.86 min and 1.45 min. Because the gas chromatographic signal response of acetal is weak, its peak area is small. Compared with the standard, it can be qualitatively identified as the gas chromatographic response peaks of the organic products acetaldehyde and acetal.

[0132] Test Example 14: The effect of light wavelength on the performance of photocatalytic ethanol dehydrogenation reaction.

[0133] To further explore the correlation between light absorption and catalytic performance, this invention systematically investigated the apparent quantum yield (AQY) of the Rh-Cs2AgBiBr6 / CdS photocatalyst under monochromatic light irradiation at different wavelengths. Figure 14 5 mg of photocatalyst (sample from Example 7) was weighed and dispersed in 5 mL of ethanol, then added to a 62 mL Schlenk glass reaction tube. Oxygen was effectively removed from the reaction system by repeated cycles of liquid nitrogen freezing-vacuum evacuation-room-temperature dissolution (freeze-evacuate-dissolve), followed by purging with argon as an inert atmosphere. Subsequently, monochromatic LED light at different wavelengths (405 nm, 500 nm, 520 nm, 590 nm, and 620 nm) with a light intensity of 3 mW / cm² was used. 2 The suspension was irradiated with light for 4 hours as the light source for the photocatalytic reaction. Hydrogen products were detected by gas chromatography. The apparent quantum yield (AQY) under different light sources was obtained. Experimental results showed that the AQY trend highly matched the light absorption characteristics of the CdS component. Under 405 nm monochromatic light excitation, the catalyst exhibited the best hydrogen production performance, with an AQY of 22.56%.

[0134] The formula for calculating the apparent quantum yield (AQY) of photocatalytic ethanol dehydrogenation is as follows:

[0135] AQY (%) = [(2 × r × N) a ) / (I × a) × 100%

[0136] R: The formation rate of the target product (acetaldehyde) (mol / s) -1 ); N a : Number of electrons required to generate a target product molecule; I: Intensity of monochromatic light irradiating the catalyst surface, expressed as photon flux density (photons m). -2 ·s -1 A: Effective light-illuminated area of ​​the catalyst (m²) 2 ); a is the illuminated area.

[0137] Test Example 15: Stability Study of Photocatalysts.

[0138] In catalytic reactions, the stability of the photocatalyst is crucial for its practical application. Therefore, this invention characterizes the stability of the Rh-Cs2AgBiBr6 / CdS photocatalyst before and after the photocatalytic reaction. For example... Figure 15As shown, the peak shape and position of the XRD pattern did not change significantly before and after the photocatalytic dehydrogenation reaction, indicating that the crystal form and crystallinity of the photocatalyst did not change significantly. This result indicates that Rh-Cs2AgBiBr6 / CdS exhibits satisfactory crystal structure stability in this system.

[0139] Test Example 16: Study on the long-term stability and cycle stability of photocatalysts.

[0140] To evaluate the stability of the Rh-Cs2AgBiBr6 / CdS photocatalytic ethanol dehydrogenation system under long-term light irradiation, this invention conducted continuous light irradiation experiments and used the water displacement method to quantitatively measure the volume of hydrogen gas produced during the reaction. Figure 16 As shown in Figure a, the photocatalytic hydrogen production activity gradually increased within the first 10 hours of the reaction; after 10 hours, the ethanol dehydrogenation capacity continued to increase, but the reaction rate decreased to some extent. After nearly 60 hours of continuous illumination, the catalytic system did not show complete deactivation and maintained a certain level of catalytic activity. The results indicate that although the hydrogen production rate gradually decreased with increasing reaction time, the composite photocatalyst could still continuously drive the ethanol dehydrogenation reaction under long-term illumination, demonstrating good photocatalytic stability. In the context of industrial applications, the cyclic operation capability of the catalytic system and the regeneration performance of the catalyst have a crucial impact on its long-term application; therefore, in-depth evaluation of these performance parameters is of great significance for the practical feasibility and sustainability of photocatalytic technology. Figure 16 As shown in b, the Rh-Cs2AgBiBr6 / CdS catalyst exhibits good stability in the cyclic photocatalytic ethanol dehydrogenation reaction. In this experiment, a 4-hour reaction cycle was used, with the ethanol solution replaced after each cycle. A simulated solar irradiance (100 mW·cm⁻¹) was applied. -2 Under these conditions, after four cycles, the ethanol dehydrogenation activity of the catalyst decreased slightly, but still remained above 80% of the initial activity, indicating that it has excellent cyclic reaction stability.

[0141] Test Example 17: Morphological stability of the catalyst after reaction (SEM).

[0142] Figure 17Images a and 17b show SEM images of the Rh-Cs2AgBiBr6 / CdS photocatalyst before and after the photocatalytic dehydrogenation of ethanol. Before the reaction, Cs2AgBiBr6 nanoparticles were observed to be uniformly loaded on the surface of CdS nanorods, with good contact at the interface, exhibiting an effective heterojunction composite structure. After the reaction, the morphology and size of the catalyst did not change significantly, and no obvious structural damage or aggregation was observed. The results indicate that Rh-Cs2AgBiBr6 / CdS possesses good structural stability during the photocatalytic reaction. This morphology retention ability helps maintain catalytic active sites and promotes electron transport during the reaction, playing an important role in the long-term cycling performance of the catalyst.

[0143] Test Example 18: Reaction Mechanism Study.

[0144] To elucidate the key active species in the photocatalytic dehydrogenation of ethanol, this invention systematically studied the Rh-Cs2AgBiBr6 / CdS system using free radical quenching experiments. 5 mg of photocatalyst (sample from Example 7) was dispersed in 5 mL of ethanol. Then, 10 μL of 2,2,6,6-tetramethylpiperidine oxide (TEMPO), 5 mg of potassium iodide (KI), 5 mg of carbon tetrachloride (CCl4), 10 μL of 5,5-dimethyl-1-pyrrolidone-N-oxide (DMPO), and 10 μL of butylated hydroxytoluene (BHT) were added as sacrificial agents, respectively, to act as holes (h... + ), electron (e - Chemical quenchers, including active carbon radicals (C·) and superoxide radicals, were introduced. These quenchers were then added to a 62 mL Schlenk glass reaction tube. Oxygen was effectively removed from the reaction system through repeated cycles of liquid nitrogen freezing, vacuum evacuation, and room temperature dissolution (freeze-evacuate-dissolve), followed by purging with argon as an inert atmosphere. The suspension was irradiated for 4 h using a 300 W xenon lamp (λ > 420 nm) as the light source for the photocatalytic reaction. Gas phase products were detected using gas chromatography. The introduction of these quenchers aims to capture reactive intermediates or free radicals generated in the photocatalytic ethanol dehydrogenation reaction, contributing to the understanding of the photocatalytic process and mechanism. Figure 18 As shown, the photocatalytic activity was completely suppressed after the addition of TEMPO, indicating that free radicals play a crucial role in the reaction. Meanwhile, h + / e - Both the quenching of carbon-center free radicals and the quenching of carbon-center free radicals significantly reduced the hydrogen production rate, indicating that these active species jointly participated in the catalytic process. The presence of carbon-center free radicals was further confirmed by in-situ electron paramagnetic resonance (EPR) spectroscopy using DMPO as a spin trap. Figure 18b), a distinct six-fold characteristic split signal (g=2.006) can be observed under visible light illumination, and its hyperfine coupling constant (a) N =15.1 G, a H =21.8G) is consistent with the standard spectrum of DMPO-carbon radical complex. Combined with the fact that this EPR signal was not detected under dark conditions, it can be inferred that photogenerated holes preferentially initiate the α-CH bond in the ethanol molecule, triggering an oxidative dehydrogenation process to generate the ·CH3CHOH radical intermediate. This result not only confirms the generation of carbon radicals but also reveals their crucial role in CH bond activation and subsequent dehydrogenation reactions, providing direct evidence for understanding the reaction mechanism.

[0145] Summary of Implementation Examples:

[0146] 1. Excellent stability and integrity verification:

[0147] The excellent structural, chemical, and morphological stability of Cs2AgBiBr6 materials and their composites under harsh reaction conditions (different atmospheres, light irradiation, and polar solvents) was systematically characterized and demonstrated (using XRD, XPS, SEM, etc.). This solves the structural degradation problem of halide perovskite materials in polar solvents, which is often faced in photocatalytic applications, and lays a solid foundation for their practical application.

[0148] 2. Performance optimization and stability breakthroughs:

[0149] By precisely controlling the loading of Cs₂AgBiBr₆ (10 wt% being optimal) and introducing Rh cocatalyst (4 wt% being optimal), an order-of-magnitude improvement in photocatalytic performance was achieved. The optimal Rh-Cs₂AgBiBr₆ / CdS catalyst achieved a hydrogen production rate as high as 49.15 mmol g⁻¹. -1 h -1 This catalyst demonstrates significantly superior performance compared to single-component catalysts, precursor mixtures, and other similar composite catalysts (such as Cs3Bi2Br9 / CdS), showcasing the unique synergistic effect and performance advantages of this system. Furthermore, this research encompasses a comprehensive evaluation of wavelength dependence (AQY up to 22.56% @405 nm), full-spectrum utilization, long-term (60 h) performance, and cycling stability (activity maintained >80% after 4 cycles), proving that this catalyst system not only possesses excellent initial activity but also exhibits good durability and promising practical application prospects.

[0150] 3. Product selectivity control:

[0151] This invention reveals the precise control of reaction pathways by catalyst structure: the Cs2AgBiBr6 / CdS heterojunction exhibits high selectivity (99.1%) for acetal, while the introduction of Rh modulates the adsorption behavior of intermediates, transforming the product distribution into a mixture of acetaldehyde (60.2%) and acetal (39.8%). This proactive control of liquid-phase product selectivity through catalyst design possesses significant scientific value and innovative applications.

[0152] 4. In-depth mechanistic insights:

[0153] Through systematic free radical capture experiments and EPR tests, the carbon-centered free radical (·CH3CHOH) was clearly verified for the first time in this system as a key active intermediate in the ethanol dehydrogenation process. This revealed that the reaction follows a free radical mechanism of hole-preferred triggering homolytic cleavage of α-CH bonds, providing a key theoretical basis for understanding the nature of the reaction and subsequent catalyst design.

[0154] The above are merely a few preferred embodiments of the present invention, described in a relatively specific and detailed manner, but they should not be construed as limiting the scope of protection of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A perovskite composite photocatalyst for photocatalytic ethanol dehydrogenation, characterized in that, The composite photocatalyst comprises CdS nanorods and active components supported on the surface of the CdS nanorods; The active component is Cs2AgBiBr6.

2. The composite photocatalyst according to claim 1, characterized in that, The active component Cs2AgBiBr6 loaded on the surface of CdS nanorods is formed by the precursors CsBr, AgBr and BiBr3 through a vacuum in-situ growth method.

3. The composite photocatalyst according to claim 1, characterized in that, The loading of Cs2AgBiBr6 is 5% to 15% of the mass of the CdS nanorods.

4. The composite photocatalyst according to claim 1, characterized in that, The composite photocatalyst is further supported with a metal co-catalyst, which is selected from Pt, Rh, and Ni; the loading of the metal co-catalyst, based on the mass of the metal element, is 2% to 5% of the total mass of the composite photocatalyst.

5. The method for preparing the composite photocatalyst according to any one of claims 1-4, characterized in that, Includes the following steps: (a) Preparation of CdS nanorods and metal halide precursors; (b) The CdS nanorods and the precursor are dispersed in a mixed organic solvent composed of dichloromethane and toluene, and ultrasonically treated for more than 10 minutes to form a uniform suspension; (c) Place the suspension in a Schlenk tube and perform a cycle of liquid nitrogen freezing-vacuum evacuation-room temperature dissolution at least twice using a double-row tube system, and then stir under vacuum or inert atmosphere for 20 to 30 min. (d) The system treated in step (c) is heated in an oil bath at 100 °C to 110 °C and all organic solvents are removed under vacuum to obtain the composite photocatalyst.

6. The preparation method according to claim 5, characterized in that, The process includes step (e) after step (d): collecting the obtained composite photocatalyst by centrifugation, washing it with diethyl ether, and then drying it under vacuum at 60 °C.

7. The preparation method according to claim 5, characterized in that, When a metal co-catalyst is supported, the following photodeposition step is also included after step (d): 1) Disperse the composite photocatalyst obtained in step (d) in ethanol; 2) Add an ethanol solution containing a metal co-catalyst precursor, wherein the metal co-catalyst precursor is chloroplatinic acid hexahydrate, rhodium chloride trihydrate, or nickel chloride hexahydrate; 3) Perform the liquid nitrogen freezing-vacuum evacuation-room temperature dissolution cycle on the mixed system at least twice; 4) Irradiate with a light source with a wavelength greater than 420 nm for 1 to 2 hours in an inert atmosphere; 5) Centrifuge to collect the product and dry it to obtain a composite photocatalyst supported on a metal co-catalyst.

8. A method for photocatalytic dehydrogenation of ethanol to prepare acetaldehyde, acetal, and hydrogen, characterized in that, At least the following steps are included: Ethanol is brought into contact with the composite photocatalyst according to any one of claims 1-4 and reacted under anaerobic conditions and light irradiation.

9. The method according to claim 8, characterized in that, The illumination uses visible light with a wavelength greater than or equal to 420 nm, and the illumination intensity is 100 mW / cm². 2 Up to 400 mW / cm 2 The reaction is carried out at room temperature for a time of 1 h to 60 h.

10. The application of the composite photocatalyst as described in any one of claims 1-4 in photocatalytic hydrogen production or photocatalytic alcohol dehydrogenation reaction.

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