Preparation method and application of an assembled structure of rod-shaped metal oxide clusters

Abstract

This invention relates to a method for preparing and applying an assembled structure of rod-shaped metal oxide clusters, belonging to the field of inorganic nanophotocatalytic materials. Addressing the problems of disordered morphology, insufficient exposure of active sites, and low selectivity for CO2 reduction in existing photocatalysts, this invention provides the following preparation method: A polyacid is dissolved in a mixed solvent to obtain solution A; an ammonia source is added and stirred to obtain solution B; after hydrothermal treatment, the solution is centrifuged and dried to obtain the assembled structure of rod-shaped metal oxide clusters. This method is mild, with controllable parameters, and the resulting product has a regular morphology and good dispersibility. When used as a photocatalyst for CO2 reduction, this material exhibits excellent CO generation rate and selectivity under simulated sunlight irradiation, and good cycle stability, making it widely applicable in photocatalytic CO2 reduction, energy conversion, and carbon recycling.

Description

Technical Field

[0001] This invention relates to the field of photochemical materials technology, specifically to a method for preparing and applying an assembly structure of rod-shaped metal oxide clusters. Background Technology

[0002] With the intensification of global climate change and the increasing prominence of fossil fuel depletion, CO2 emission reduction and conversion have become core research directions in the energy and environment fields. CO, as a high-value carbon-based intermediate, is both a key raw material in chemical processes and a clean fuel or syngas component; therefore, the highly selective reduction of CO2 to CO has significant economic and environmental value. Photocatalytic reduction technology, which can utilize solar energy to drive CO2 conversion at room temperature and pressure, and requires only CO2, water, and solar energy without additional high-energy input or fossil fuel consumption, has become the preferred technology in the current CO2 conversion field. Metal oxides, due to their high chemical stability, low preparation cost, and strong controllability, are one of the mainstream catalyst materials in the field of photocatalytic CO2 reduction.

[0003] Existing metal oxides (such as traditional materials like TiO2 and ZnO) have wide band gaps, allowing them to absorb only ultraviolet light from sunlight (which accounts for less than 4% of total solar energy). Their absorption capacity for visible and near-infrared light is extremely poor, resulting in solar energy conversion efficiency generally below 1%, which cannot meet the energy utilization efficiency requirements of practical applications.

[0004] Phosphotungstic acid (H3PMo) 12 O 40 As a typical polyoxometalate, its molecule contains Mo-O-Mo bridging bonds and terminal oxygen groups, forming a unique "metal-oxygen cluster" electronic conjugation system. The band gap can be tuned to 2.0~2.8 eV (far narrower than TiO2), which can effectively absorb visible light (accounting for 43% of solar energy) and even the edge of near-infrared light, directly improving solar energy utilization and solving the bottleneck of traditional oxides "only absorbing ultraviolet light". The rod-shaped structure formed by directional assembly, compared with disordered particles, has an aspect ratio (which can be adjusted by the ratio of acetone, ethanol, deionized water, and solvent) that can enhance light scattering and multiple reflection effects. After light enters the gaps between the rod-shaped structures, it can be absorbed multiple times by the catalyst surface, reducing light escape and further improving light capture efficiency. Summary of the Invention

[0005] In order to solve the problems of the prior art, the present invention provides a method for preparing and applying an assembly structure of rod-shaped metal oxide clusters.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: Firstly, a method for preparing an assembled structure of rod-shaped metal oxide clusters, comprising the following steps: S1, Dissolve the polyacid in a mixed solvent and stir until fully dissolved to obtain mixed solution A; S2, Add an ammonia source to mixed solution A and stir to obtain mixed solution B; S3, place the mixed solution B in a reaction vessel for hydrothermal treatment to obtain mixed solution C; S4. The mixed solution C is centrifuged, the precipitate is dried, and the assembled rod-shaped structure of metal oxide clusters is obtained.

[0007] In one specific embodiment of the first aspect, the polyacid in step S1 is one or more of phosphomolybdic acid, phosphotungstic acid, and silicotungstic acid, and the mass of the polyacid is 10 mg to 30 mg.

[0008] In one specific embodiment of the first aspect, the mixed solvent in step S2 is one or more of ethanol, acetone, and deionized water, and the volume of the mixed solvent is 1 mL to 20 mL.

[0009] In one specific embodiment of the first aspect, the stirring temperature in step S1 is 15 ℃ to 35 ℃.

[0010] In one specific embodiment of the first aspect, the ammonia source in step S2 is one or more of ammonia water, urea, and ammonia methanol, and the volume of the ammonia source is 0.1 mL to 0.5 mL.

[0011] In one specific embodiment of the first aspect, the temperature of the hydrothermal treatment in step S3 is 150 ℃~250 ℃, and the time is 10 h~20 h.

[0012] In one specific embodiment of the first aspect, the centrifugation speed in step S4 is 8000 rpm to 10000 rpm, and the centrifugation time is 3 min to 5 min; the drying is vacuum drying or freeze drying, the vacuum drying temperature is 50 ℃ to 70 ℃ and the time is 12 h to 20 h, and the freeze drying time is 12 h to 20 h.

[0013] Secondly, an assembled rod-shaped structure of a metal oxide cluster is prepared by a method for preparing an assembled rod-shaped metal oxide cluster.

[0014] In one specific embodiment of the second aspect, the assembled rod-shaped structure of metal oxide clusters is used as a catalyst for the photocatalytic reduction of carbon dioxide.

[0015] The beneficial effects of this invention are as follows: 1. This invention features a mild process, simple operation, controllable parameters, and environmental friendliness. The method uses polyoxometalates as precursors, dissolved in a mixed solvent of ethanol, acetone, and deionized water. Ammonia source is added to adjust the pH value, inducing directional assembly. A subsequent hydrothermal treatment achieves controllable growth of rod-shaped structures. The entire preparation process requires no complex equipment, no high-temperature calcination, and no surfactants or templates, resulting in low cost and high reproducibility. By optimizing key parameters such as the type and amount of polyoxometalates, solvent ratio, ammonia source addition, and hydrothermal temperature and time, the aspect ratio, crystallinity, and dispersibility of the rod-shaped products can be precisely controlled. The resulting rod-shaped metal oxide clusters exhibit regular morphology, uniform size, and stable structure, overcoming the technical bottlenecks of disordered morphology and insufficient exposure of active sites commonly found in existing metal oxide photocatalysts. Furthermore, the solvents used in the preparation process are recyclable, and the waste liquid after centrifugation and washing does not contain highly toxic substances, meeting the requirements of green chemistry development and facilitating large-scale production and practical application. 2. The rod-shaped metal oxide cluster assembly structure prepared in this invention, as a photocatalyst, exhibits excellent light absorption capacity, carrier separation efficiency, product selectivity, and cycle stability in the photocatalytic reduction of carbon dioxide. First, this material uses polyacids such as phosphotungstic acid and phosphomolybdic acid as active centers. Its "metal-oxygen cluster" electronic conjugation system can tune the band gap to 2.0 eV–2.8 eV, effectively absorbing visible light and even near-infrared light edges, breaking through the photoresponse limitation of traditional metal oxides (such as TiO2 and ZnO) which can only absorb ultraviolet light, significantly improving solar energy utilization. Second, the unique rod-shaped structure provides the material with a one-dimensional directional electron transport path, shortening the distance photogenerated carriers migrate from the bulk phase to the surface. Simultaneously, the light scattering effect of the rod array reduces light escape, synergistically reducing carrier recombination rate and improving quantum efficiency. Third, acetone or ethanol solvents optimize the cluster dispersion state, and the introduction of an ammonia source modulates the surface chemical environment, reducing defect recombination centers and enabling photogenerated electrons to participate more effectively in the CO2 reduction reaction. Experimental data show that the catalyst can achieve a CO production rate of 18.5 μmol·g under simulated sunlight irradiation. -1 ·h -1 The CO selectivity reaches 94%, and the activity retention rate still exceeds 92% after 5 cycles, far superior to traditional amorphous metal oxide catalysts. Therefore, this invention not only provides a high-performance, highly stable novel catalytic material for the photocatalytic reduction of CO2 to CO, but can also be extended to cutting-edge fields such as new energy conversion, carbon recycling, and artificial photosynthesis, providing a practical and feasible technical path to achieve the "dual carbon" goal. Attached Figure Description

[0016] Figure 1 This is a scanning electron microscope (SEM) image of the photocatalyst in Example 1 of the present invention.

[0017] Figure 2 This is a performance test diagram of the photocatalyst in Example 1 of the present invention.

[0018] Figure 3 This is a scanning electron microscope (SEM) image of the photocatalyst in Example 2 of the present invention.

[0019] Figure 4 This is a performance test diagram of the photocatalyst in Example 2 of the present invention.

[0020] Figure 5 This is a scanning electron microscope (SEM) image of the photocatalyst in Example 3 of the present invention.

[0021] Figure 6 This is a performance test of the photocatalyst in Example 3 of the present invention. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] like Figures 1 to 6 The method for preparing and applying an assembly structure of a rod-shaped metal oxide cluster is shown.

[0024] S1 dissolves a certain amount of polyacid in a mixed solvent of the appropriate proportion and stirs it under appropriate conditions until it is fully dissolved, thus obtaining a mixed solution A.

[0025] S2 Add an appropriate amount of ammonia solution to the mixed solution A obtained in S1 and stir to obtain mixed solution B.

[0026] S3 places the mixed solution B obtained in S2 into a reaction vessel for hydrothermal treatment to obtain mixed solution C.

[0027] S4 involves centrifuging and drying the mixed solution C obtained in S3 to obtain an assembled rod-shaped catalyst of metal oxide clusters.

[0028] In this invention, the preferred mass of the polyacid is 10-100 mg, most preferably 20-50 mg. The polyacid is preferably one of phosphotungstic acid, phosphomolybdic acid, and silicotungstic acid. The preferred solvent volume is 10-50 mL, most preferably 10-30 mL. The solvent is preferably one of ethanol, acetone, deionized water, and a mixture of ethanol and acetone. The ammonia solution is preferably ammonia water, with a preferred volume of 0.05 mL-2 mL, most preferably 0.1 mL-0.15 mL. The preferred hydrothermal temperature is 150℃-250℃, most preferably 175℃-200℃. The preferred centrifugation speed is 6000 rpm-10000 rpm, most preferably 8000 rpm-10000 rpm.

[0029] This invention also provides the application of the rod-shaped metal oxide cluster photocatalyst described above in photocatalytic CO2 reduction. Firstly, a high-transmittance quartz reactor is preferred as the experimental photocatalytic reactor to ensure efficient penetration and application of subsequent light to the reaction system. Subsequently, the photocatalyst is loaded and pretreated: preferably, the photocatalyst provided by this invention is uniformly dispersed at the bottom of a quartz reactor filled with deionized water. Ultrasonic treatment is used to fully disperse the catalyst particles, preventing agglomeration that could affect reaction activity. After ultrasonication, the reactor is dried overnight under suitable conditions, ultimately forming a uniformly distributed catalyst film at the bottom of the reactor, providing stable and sufficient active sites for the gas-solid catalytic reaction.

[0030] After the catalyst film is prepared, in order to completely eliminate the interference of air in the reactor to the experiment, a mixture of H2O vapor and high-purity CO2 is continuously introduced into the quartz reactor. After the gas introduction operation reaches the preset requirements and ensures that the air in the reactor has been completely purged and fully filled with the mixed gas, the quartz reactor is quickly sealed to maintain the airtightness of the reaction system.

[0031] Next, the photocatalytic reaction is initiated: a sealed quartz reactor filled with a mixture of H2O vapor and high-purity CO2 is precisely placed under a Zhongjiao Jinyuan xenon lamp light source (this xenon lamp has been pre-calibrated for power intensity and is equipped with a special filter that can effectively simulate the full spectrum characteristics of sunlight) to provide the reaction with illumination conditions that meet the actual application scenario; at the same time, the circulating cooling water system is turned on, and by adjusting the flow rate and temperature of the cooling water, the system temperature is kept stable within the set range throughout the reaction process to avoid temperature fluctuations caused by heat generation from light affecting reaction efficiency and product selectivity.

[0032] During the reaction, an online gas chromatograph (model: HF-901, manufacturer: Huifen Instruments Co., Ltd.) was used to monitor the reaction gas at the reactor outlet in real time. Through the instrument's built-in analysis function, the qualitative identification and quantitative detection of the composition of the reaction gas were completed, thereby accurately grasping the CO2 conversion, product types and concentration changes of each component during the reaction process, providing comprehensive and reliable experimental data for subsequent photocatalyst performance evaluation and reaction mechanism research.

[0033] The present invention will be further illustrated below through typical embodiments. Example 1

[0034] Preparation method and photocatalytic performance testing of an assembled structure of rod-shaped metal oxide clusters S1 Dissolves 20 mg of phosphotungstic acid in 10 mL of acetone and stirs until fully dissolved to obtain a mixed solution; S2 Add 0.25 ml of ammonia water to the mixed solution obtained in step S1 while stirring and stir for 5 min; S3. Transfer the solution stirred in step S2 into a polytetrafluoroethylene liner, and seal the liner in a stainless steel high-pressure reactor. S4. Place the stainless steel high-pressure reactor from step S3 into an oven and react at 180 °C for 6 hours. After obtaining the product, wash it three times with water or by centrifugation at 10,000 rpm for 2 minutes. Then dry it in a vacuum at 60 °C to obtain the rod-shaped metal cluster photocatalyst. S5. The 10 mg phosphotungstic acid rod-shaped photocatalyst obtained in step S4 is uniformly dispersed at the bottom of a quartz reactor (a quartz reactor with a volume of 180 ml and high light transmittance is used as a photocatalytic reactor) containing 15 ml of deionized water, and the quartz reactor is uniformly dispersed at the bottom. The photoreactor is placed in an oven at 60 ℃ overnight. After drying, a uniformly distributed catalyst film is obtained at the bottom of the photoreactor. In step S6, a mixture of H2O vapor and high-purity CO2 was continuously passed through the photocatalytic reactor containing the catalyst obtained in step S5 for 30 minutes. The quartz reactor filled with the H2O vapor and high-purity CO2 mixture was then irradiated under a xenon lamp to simulate the full spectrum of sunlight. The reaction temperature was maintained at 15°C using circulating cooling water. Qualitative and quantitative analysis of the reaction gas composition was performed using an online gas chromatograph (HF~901, Huifen Instruments Co., Ltd.), yielding the attached... Figure 2 Performance test chart in the middle. Example 2

[0035] Preparation method and photocatalytic performance testing of an assembled structure of rod-shaped metal oxide clusters S1 Dissolves 10 mg of phosphotungstic acid in 15 mL of acetone and stirs until fully dissolved to obtain a mixed solution; S2 Add 0.5 ml of ammonia water to the mixed solution obtained in step S1 while stirring and stir for 5 min; S3. Transfer the solution stirred in step S2 into a polytetrafluoroethylene liner, and seal the liner in a stainless steel high-pressure reactor. S4. Place the stainless steel high-pressure reactor from step S3 into an oven and react at 200 °C for 12 hours. After obtaining the product, wash it three times with water or by centrifugation at 10,000 rpm for 2 minutes. Then dry it in a vacuum at 60 °C to obtain the rod-shaped metal cluster photocatalyst. S5. The 10 mg phosphotungstic acid rod-shaped photocatalyst obtained in step S4 is uniformly dispersed at the bottom of a quartz reactor (a quartz reactor with a volume of 180 ml and high light transmittance is used as a photocatalytic reactor) containing 15 ml of deionized water, and the quartz reactor is uniformly dispersed at the bottom. The photoreactor is placed in an oven at 60 ℃ overnight. After drying, a uniformly distributed catalyst film is obtained at the bottom of the photoreactor. S6 continuously introduces H2O steam and high-purity CO into the catalyst-containing photocatalytic reactor obtained in step S5. - The mixture of H2O vapor and high-purity CO2 was irradiated for 30 min under a xenon lamp to simulate the full spectrum of sunlight, and the reaction temperature was maintained at 15 °C using circulating cooling water. Qualitative and quantitative analysis of the reaction gas composition was performed using an online gas chromatograph (HF~901, Huifen Instruments Co., Ltd.), yielding the following results: Figure 4 Performance test chart in the middle. Example 3

[0036] Preparation method and photocatalytic performance testing of an assembled structure of rod-shaped metal oxide clusters S1 Dissolves 30 mg of phosphotungstic acid in 20 mL of ethanol and stirs until fully dissolved to obtain a mixed solution; S2 Add 0.2 ml of ammonia water to the mixed solution obtained in step S1 while stirring and stir for 5 min; S3. Transfer the solution stirred in step S2 into a polytetrafluoroethylene liner, and seal the liner in a stainless steel high-pressure reactor. S4. The stainless steel high-pressure reactor from step S3 is placed in an oven and reacted at 150 °C for 10 hours. After obtaining the product, it is washed three times with water or by centrifugation at 10,000 rpm for 2 minutes. Then it is dried in a vacuum at 60 °C to obtain a rod-shaped metal cluster photocatalyst. S5. The 10 mg phosphotungstic acid rod-shaped photocatalyst obtained in step S4 is uniformly dispersed at the bottom of a quartz reactor (a quartz reactor with a volume of 180 ml and high light transmittance is used as a photocatalytic reactor) containing 15 ml of deionized water, and the quartz reactor is uniformly dispersed at the bottom. The photoreactor is placed in an oven at 60 ℃ overnight. After drying, a uniformly distributed catalyst film is obtained at the bottom of the photoreactor. S6. The catalyst-containing photocatalytic reactor obtained in step S5 is continuously purged with a mixture of H2O vapor and high-purity CO2 for 30 minutes. The quartz reactor filled with the H2O vapor and high-purity CO2 mixture is then irradiated under a xenon lamp to simulate the full spectrum of sunlight. The reaction temperature is maintained at 15 °C using circulating cooling water. Qualitative and quantitative analysis of the reaction gas composition is performed using an online gas chromatograph (HF~901, Huifen Instruments Co., Ltd.), yielding the attached... Figure 6 Performance test chart in the middle.

[0037] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing an assembled structure of rod-shaped metal oxide clusters, characterized by, Includes the following steps: S1, Dissolve the polyacid in a mixed solvent and stir until fully dissolved to obtain mixed solution A; S2, Add an ammonia source to mixed solution A and stir to obtain mixed solution B; S3, place the mixed solution B in a reaction vessel for hydrothermal treatment to obtain mixed solution C; S4. The mixed solution C is centrifuged, the precipitate is dried, and the assembled rod-shaped structure of metal oxide clusters is obtained.

2. The method of claim 1, wherein the method further comprises: The polyacid mentioned in step S1 is one or more of phosphomolybdic acid, phosphotungstic acid, and silicotungstic acid, and the mass of the polyacid is 10 mg to 30 mg.

3. The method for preparing an assembled structure of rod-shaped metal oxide clusters according to claim 1, characterized in that: The mixed solvent mentioned in step S2 is one or more of ethanol, acetone, and deionized water, and the volume of the mixed solvent is 1 mL to 20 mL.

4. The method for preparing an assembled structure of rod-shaped metal oxide clusters according to claim 1, characterized in that: The stirring temperature in step S1 is 15 ℃~35 ℃.

5. The method for preparing an assembled structure of rod-shaped metal oxide clusters according to claim 1, characterized in that: The ammonia source mentioned in step S2 is one or more of ammonia water, urea, and ammonia methanol, and the volume of the ammonia source is 0.1 mL to 0.5 mL.

6. The method for preparing an assembled structure of rod-shaped metal oxide clusters according to claim 1, characterized in that: The hydrothermal treatment in step S3 is performed at a temperature of 150 ℃ to 250 ℃ for a time of 10 h to 20 h.

7. The method for preparing an assembled structure of rod-shaped metal oxide clusters according to claim 4, characterized in that: In step S4, the centrifugation speed is 8000 rpm to 10000 rpm and the centrifugation time is 3 min to 5 min; the drying is vacuum drying or freeze drying. The vacuum drying temperature is 50 ℃ to 70 ℃ and the time is 12 h to 20 h, and the freeze drying time is 12 h to 20 h.

8. An assembled rod-like structure of a metal oxide cluster, characterized in that, The rod-shaped metal oxide cluster assembly structure was prepared using the method described in any one of claims 1 to 7.

9. The application of the assembled rod-shaped structure of the metal oxide cluster as described in claim 8 as a catalyst for the photocatalytic reduction of carbon dioxide.

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