CeO2 loaded monatomic catalyst with one-dimensional nanofiber structure as well as preparation method and application of CeO2 loaded monatomic catalyst

Abstract

The invention discloses a one-dimensional nanofiber structure CeO2 loaded monatomic catalyst as well as a preparation method and application thereof, and belongs to the technical field of environmental functional materials. The preparation method of the catalyst comprises the following steps: firstly, dissolving a cerium source in a mixed solvent of ultrapure water and absolute ethyl alcohol to obtain a solution A; dissolving a precipitator in a mixed solvent of ultrapure water and absolute ethyl alcohol to obtain a solution B; pouring the solution B into the solution A in a stirring state, and carrying out stirring reaction, filtering, washing and calcining to obtain a CeO2 carrier; then ultrasonically dispersing the CeO2 carrier in absolute ethyl alcohol, adding a rhodium source in the stirring process, stirring and reacting at room temperature, drying and calcining to obtain the CeO2 loaded monatomic catalyst with the one-dimensional nanofiber structure. Rhodium in the catalyst exists in a monatomic form, so that the utilization rate of precious metal is increased, the cost is reduced, the catalytic activity is improved, and the catalyst can be used for solar photo-thermal catalysis of carbon dioxide methanation.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental functional materials, and in particular relates to a one-dimensional nanofiber structure CeO2-loaded single-atom catalyst, a preparation method and an application thereof. Background Art

[0002] Carbon dioxide (CO2) is a major greenhouse gas. Traditional carbon capture and storage (CCS) technologies face high energy consumption and potential geological risks, necessitating the development of innovative approaches that combine carbon reduction with value-added capabilities. With the acceleration of industrialization, fuel issues have also become a global challenge. Currently, the transition to renewable energy is insufficient, and extreme weather and geopolitical conflicts are further disrupting energy supply chains. Many countries are facing energy shortages and rising industrial costs, leading to a growing demand for accelerating green transformation to alleviate the structural energy crisis.

[0003] Solar energy, with an annual surface irradiation exceeding 100,000 TW, is the ultimate clean energy source. Against the backdrop of the dual pressures of fossil energy depletion and the dramatic increase in greenhouse gases, utilizing solar energy to convert H₂O and CO₂ into solar fuels is a highly promising method for solar energy storage and carbon recycling. This process achieves a carbon-neutral cycle, with the CO₂ released from fuel combustion being converted and reused to meet the requirements of sustainable development. Its efficient utilization is a key path to solving the energy dilemma. However, the intermittent nature and low energy density of solar energy necessitate the development of storable energy carriers. Current solar-driven conversion pathways include photocatalysis, thermocatalysis, and synergistic photothermal catalysis. Photothermal catalytic materials combine the advantages of photocatalysis and thermocatalysis. While efficiently absorbing sunlight and converting it into heat energy, they also generate a photothermal effect within the material itself or locally. The synergistic effect of light and heat significantly enhances the efficiency and rate of the catalytic reaction.

[0004] While various catalysts have made progress, conflicts in activity, selectivity, stability, and cost control are becoming increasingly prominent. Reaction conditions restrict technical and economic feasibility, and the complex and yet-to-be-elucidated mechanisms of catalyst deactivation severely hinder their industrial application. Summary of the Invention

[0005] In response to the above technical problems, the present invention aims to efficiently catalyze CO2 methanation using solar energy, and proposes a one-dimensional nanofiber structured CeO2-loaded single-atom catalyst and its preparation method and application, providing a new approach and method for the efficient application of solar energy.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the purposes of the present invention is to provide a method for preparing a one-dimensional nanofiber structure CeO2-supported single-atom catalyst, comprising the following steps:

[0008] (1) dissolving a cerium source in a mixed solvent of ultrapure water and anhydrous ethanol to obtain a solution A, wherein the volume ratio of the ultrapure water to the anhydrous ethanol is 1:1;

[0009] Dissolving the precipitant in a mixed solvent of ultrapure water and anhydrous ethanol to obtain solution B, wherein the volume ratio of the ultrapure water to the anhydrous ethanol is 1:1;

[0010] Pour solution B into solution A under stirring, react with stirring, filter, wash and calcine to obtain CeO2 carrier;

[0011] (2) Ultrasonic dispersion of the CeO2 carrier in anhydrous ethanol, adding a rhodium (Rh) source during stirring, stirring and reacting at room temperature, and then drying and calcining to obtain a one-dimensional nanofiber structured CeO2-supported single-atom catalyst.

[0012] In the present invention, by adding a rhodium source to a dispersed CeO2 carrier, rhodium atoms can be uniformly loaded on the CeO2 surface, achieving single-atom dispersion. The single-atom dispersed rhodium atoms have higher activity and utilization rate, which can significantly improve the catalytic performance of the catalyst. The one-dimensional nanofiber structure of the CeO2 carrier has a large specific surface area and abundant active sites, which can provide more adsorption and dispersion sites for rhodium atoms, thereby improving the activity of the catalyst. At the same time, the nanofiber structure of the CeO2 carrier has good thermal and mechanical stability, and can maintain structural integrity during high-temperature calcination and reaction processes, thereby improving the stability of the catalyst.

[0013] Furthermore, when preparing solution A, the usage ratio of the cerium source to the mixed solvent is (5-10) g:100 mL.

[0014] Furthermore, when preparing solution B, the ratio of the precipitant to the mixed solvent is (4-5) g:100 mL.

[0015] By controlling the amounts of cerium source and precipitant, the composition and structure of the CeO2 support can be adjusted. An appropriate amount of cerium source ensures the production and quality of CeO2, while an appropriate amount of precipitant promotes the precipitation reaction of cerium ions, forming a uniform CeO2 nanofiber structure. This structure exhibits excellent catalytic performance and stability, improving the overall performance of the catalyst. A suitable ratio ensures a thorough reaction, minimizes side reactions, and thus improves reaction efficiency and product quality. Excessive or insufficient amounts of cerium source and precipitant can lead to incomplete reaction or the formation of undesirable products, compromising catalyst performance.

[0016] Furthermore, the cerium source is cerium nitrate or cerium acetate.

[0017] Furthermore, the precipitant is ammonium carbonate or ammonium bicarbonate.

[0018] Cerium nitrate is a commonly used cerium source with good solubility and reactivity. It can undergo a uniform precipitation reaction with the precipitant to produce high-purity CeO2. Ammonium carbonate and ammonium bicarbonate, as precipitants, can react with cerium ions under mild conditions to form a uniform CeO2 nanofiber structure. This choice of precipitant improves the controllability of the reaction and product purity, thereby ensuring the quality of the catalyst. During the reaction, ammonium carbonate and ammonium bicarbonate release carbonate ions, which precipitate with cerium ions to form a uniform CeO2 nanofiber structure. This structure has excellent catalytic performance and stability, and can enhance the activity and selectivity of the catalyst.

[0019] Furthermore, in step (1), the stirring reaction time is 12 hours.

[0020] Stirring the reaction for 12 hours ensures a thorough reaction between the cerium source and the precipitant, allowing the cerium ions to fully contact the precipitant and undergo a precipitation reaction, resulting in the formation of a uniform CeO2 nanofiber structure. Sufficient reaction time improves product quality and purity, thereby ensuring catalyst performance. Prolonged stirring also makes the reaction system more uniform, promoting the uniform growth and regular arrangement of CeO2 nanofibers. This uniformity and regularity are crucial for improving the activity and stability of the catalyst.

[0021] Furthermore, in step (2), the usage ratio of the CeO2 carrier to anhydrous ethanol is (0.1-10) g: (20-100) mL.

[0022] By controlling the ratio of CeO2 support to anhydrous ethanol, the dispersion of the CeO2 support in anhydrous ethanol can be adjusted, thereby optimizing the loading of the rhodium source. An appropriate amount of anhydrous ethanol ensures good dispersion of the CeO2 support, allowing the rhodium source to be evenly loaded on the CeO2 surface, achieving single-atom dispersion. A suitable ratio ensures the loading and dispersion of the rhodium source, thereby improving the activity and stability of the catalyst. Excessive or insufficient anhydrous ethanol can lead to uneven dispersion of the CeO2 support or incomplete loading of the rhodium source, compromising catalyst performance.

[0023] Furthermore, the rhodium source is one or more of rhodium chloride solution, rhodium acetate solution and rhodium nitrate solution; and the loading amount is 0.05-5wt%.

[0024] Rhodium is a highly efficient catalyst that can significantly increase the reaction rate and selectivity of carbon dioxide methanation. By selecting an appropriate rhodium source, such as rhodium chloride solution, rhodium acetate solution, and rhodium nitrate solution, uniform dispersion and active performance of the rhodium can be ensured. An appropriate loading can ensure the activity and stability of the catalyst while avoiding the increased costs caused by excessive precious metals. Within a loading range of 0.05-5wt%, rhodium can be dispersed in the form of single atoms on the surface of the CeO2 carrier, achieving efficient catalytic activity. Single-atom dispersed rhodium atoms have higher activity and utilization rate, which can significantly improve the performance of the catalyst.

[0025] Furthermore, in step (2), the stirring reaction time at room temperature is 4-8 hours.

[0026] Stirring the reaction at room temperature for 4-8 hours ensures sufficient contact and reaction between the rhodium source and the CeO2 support, resulting in a uniform loading of the rhodium source on the CeO2 surface. Sufficient reaction time can enhance loading efficiency and ensure catalyst activity and stability. An appropriate reaction time ensures uniform dispersion and single-atom loading of the rhodium source, optimizing the catalyst's structure and performance. Too short a reaction time may result in incomplete loading, while too long a reaction time may cause rhodium atoms to aggregate, compromising catalyst performance.

[0027] Furthermore, in step (1) and step (2), the specific operating steps of the calcination are: raising the temperature from room temperature to 300-800°C at a rate of 1-5°C / min, and keeping it at this temperature for 2-6 hours, wherein step (2) is carried out under a hydrogen or nitrogen atmosphere.

[0028] The calcination process removes organic impurities and forms a stable structure between the CeO2 carrier and the loaded rhodium atoms. By controlling the calcination temperature and time, the crystal structure of CeO2 and the dispersion of rhodium atoms can be optimized, thereby improving the stability and activity of the catalyst. Appropriate calcination temperatures and times prevent excessive sintering or aggregation of the CeO2 carrier and rhodium atoms, thereby ensuring the activity and stability of the catalyst. Excessively high temperatures or prolonged calcinations can lead to catalyst deactivation or structural damage, compromising performance.

[0029] The second object of the present invention is to provide a one-dimensional nanofiber structure CeO2 loaded single atom catalyst, which is prepared using the above preparation method.

[0030] The above-described preparation method enables the preparation of a CeO2-supported single-atom catalyst with high activity, high stability, and single-atom dispersion. This catalyst exhibits excellent catalytic performance and can efficiently catalyze the carbon dioxide methanation reaction. This catalyst has significant application advantages in solar-thermal catalytic carbon dioxide methanation, enabling efficient utilization of solar energy and efficient conversion of carbon dioxide, providing an effective approach to addressing energy and environmental issues.

[0031] The third object of the present invention is to provide an application of a one-dimensional nanofiber structured CeO2-loaded single-atom catalyst in solar thermal catalytic carbon dioxide methanation.

[0032] This catalyst exhibits excellent catalytic performance under solar photothermal conditions, efficiently converting carbon dioxide into methane. Its monoatomic dispersion of rhodium atoms and one-dimensional nanofiber-structured CeO2 support significantly enhance the reaction rate and selectivity. Solar photothermal catalytic carbon dioxide methanation enables efficient solar energy utilization and a carbon-neutral cycle. This process not only reduces carbon dioxide emissions but also generates renewable methane fuel, providing an effective solution for sustainable development.

[0033] Compared with the prior art, the present invention has the following advantages and technical effects:

[0034] The preparation method of the present invention features simple conditions, few reaction-influencing factors, and easily controllable surface structures and stable performance of the resulting single-atom material. The highly dispersed single-atom form of the noble metal Rh effectively reduces the amount of noble metal used while maintaining high catalytic activity, resulting in a catalyst with higher economic value. Compared to traditional catalysts, the resulting catalyst can more efficiently and selectively generate methane.

[0035] The method provided by the present invention is simple to operate and has high universality; the catalyst has high catalytic activity, high stability and wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0037] Figure 1 This is the SEM image of the CeO2-50 carrier prepared in Example 1;

[0038] Figure 2 The SEM images (5 μm and 1 μm) of the CeO2-25 support prepared in Comparative Example 1 are shown;

[0039] Figure 3This is the SEM image of the CeO2-75 carrier prepared in Comparative Example 2;

[0040] Figure 4 TEM image of Rh-CeO2-50 prepared in Example 1;

[0041] Figure 5 XRD patterns of CeO2-25 support, CeO2-50 support and CeO2-75 support;

[0042] Figure 6 This is the photothermal catalytic performance diagram of single-atom Rh-CeO2-25 catalyst, single-atom Rh-CeO2-50 catalyst and single-atom Rh-CeO2-75 catalyst. DETAILED DESCRIPTION

[0043] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0045] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0046] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0047] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0048] The present invention provides a method for preparing a one-dimensional nanofiber structured CeO2-supported single-atom catalyst, comprising the following steps:

[0049] (1) dissolving a cerium source in a mixed solvent of ultrapure water and anhydrous ethanol to obtain a solution A; dissolving a precipitant in a mixed solvent of ultrapure water and anhydrous ethanol to obtain a solution B; pouring the solution B into the solution A under stirring, reacting with stirring, filtering, washing, and calcining to obtain a CeO2 carrier;

[0050] (2) Ultrasonic dispersion of the CeO2 carrier in anhydrous ethanol, adding a rhodium (Rh) source during stirring, stirring and reacting at room temperature, and then drying and calcining to obtain a one-dimensional nanofiber structured CeO2-supported single-atom catalyst.

[0051] In some optional embodiments of the present invention, when preparing solution A, the ratio of the cerium source to the mixed solvent is (5-10) g:100 mL, wherein the volume ratio of ultrapure water to anhydrous ethanol is 1:1. As an example, in the following preferred embodiments of the present invention, the ratio of the cerium source to ultrapure water to anhydrous ethanol is 8.6844 g:50 mL:50 mL.

[0052] In some optional embodiments of the present invention, when preparing solution B, the amount ratio of the precipitant to the mixed solvent is (4-5) g: 100 mL, wherein the volume ratio of ultrapure water to anhydrous ethanol is 1: 1. As an example, in the following preferred embodiments of the present invention, the amount ratio of the precipitant, ultrapure water, and anhydrous ethanol is 4.6123 g: 50 mL: 50 mL.

[0053] In the following preferred embodiments of the present invention, the cerium source is cerium nitrate or cerium acetate.

[0054] In some optional embodiments of the present invention, the precipitant is ammonium carbonate or ammonium bicarbonate. As an example, in the following preferred embodiments of the present invention, the precipitant is ammonium carbonate.

[0055] In the following preferred embodiments of the present invention, in step (1), the stirring reaction time is 12 hours.

[0056] In the following preferred embodiment of the present invention, in step (1), the washing is performed 3 times with deionized water.

[0057] In some optional embodiments of the present invention, in step (1), the drying is carried out at 60-80° C. for 6-12 hours. As an example, in the following preferred embodiments of the present invention, the drying temperature is 60° C. and the drying time is 12 hours.

[0058] In some optional embodiments of the present invention, in step (1), the specific operation steps of the calcination are: heating from room temperature to 300-800°C at a rate of 1-5°C / min, and holding at this temperature for 2-6 hours. As an example, in the following preferred embodiments of the present invention, the calcination heating rate is 2°C / min, the calcination temperature is 500°C, and the holding time is 4 hours.

[0059] In some optional embodiments of the present invention, in step (2), the ratio of the amount of the CeO2 carrier to the anhydrous ethanol is (0.1-10) g: (20-100) mL. As an example, in the following preferred embodiments of the present invention, the ratio of the amount of the CeO2 carrier to the anhydrous ethanol is 0.5 g: 30 mL.

[0060] In some optional embodiments of the present invention, in step (2), the rhodium source is one or more of a rhodium chloride solution, a rhodium acetate solution, and a rhodium nitrate solution; and the loading amount is 0.05-5 wt %. As an example, in the following preferred embodiments of the present invention, the rhodium source is a rhodium chloride solution, and the loading amount is 0.25 wt %. The loading amount refers to the loading amount of the rhodium source on the one-dimensional nanofibrous structure CeO2-supported single-atom catalyst.

[0061] In some optional embodiments of the present invention, in step (2), the stirring reaction time at room temperature is 4-8 hours. As an example, in the following preferred embodiments of the present invention, the stirring reaction time at room temperature is 6 hours.

[0062] In some optional embodiments of the present invention, in step (2), the specific operation steps of the calcination are: heating from room temperature to 300-800°C at a rate of 1-5°C / min under a hydrogen or nitrogen atmosphere, and holding at this temperature for 2-6 hours. As an example, in the following preferred embodiments of the present invention, the calcination heating rate is 2°C / min, the calcination temperature is 400°C, and the holding time is 3 hours.

[0063] The embodiment of the present invention further discloses a one-dimensional nanofiber structured CeO2-supported single-atom catalyst, which can be prepared using the above-mentioned preparation method.

[0064] The embodiments of the present invention also disclose a one-dimensional nanofiber structure CeO2 loaded single-atom catalyst that can be used in solar thermal catalytic carbon dioxide methanation.

[0065] Unless otherwise specified, the "room temperature" in the present invention refers to 25±2°C.

[0066] The raw materials used in the present invention are all purchased from the market.

[0067] The technical solution of the present invention is further illustrated by the following examples.

[0068] Example 1

[0069] A method for preparing a one-dimensional nanofiber structured CeO2-supported single-atom catalyst comprises the following steps:

[0070] (1) Preparation of CeO2-50 carrier: 8.6844 g (20 mmol) of cerium nitrate was dissolved in a mixed solvent of 50 mL of anhydrous ethanol and 50 mL of ultrapure water at room temperature to obtain a cerium nitrate solution; 4.6123 g (48 mmol) of ammonium carbonate was dissolved in a mixed solvent of 50 mL of anhydrous ethanol and 50 mL of ultrapure water to obtain an ammonium carbonate solution; the ammonium carbonate solution was poured into the cerium nitrate solution under stirring, and stirred at room temperature for 12 h. The solid precipitate was collected by filtration, washed three times with deionized water, dried at 60°C for 12 h, and then heated from room temperature to 500°C at a rate of 2°C / min under air conditions and kept at this temperature for 4 h to obtain a light yellow powder, which is the CeO2-50 carrier;

[0071] (2) Preparation of Rh-CeO2-50 catalyst: 0.5 g of the CeO2-50 carrier prepared in step (1) was ultrasonically dispersed in 30 mL of anhydrous ethanol, and 0.25 wt% (0.25 wt% refers to the mass percentage of the rhodium source loaded on the one-dimensional nanofiber CeO2 catalyst carrier, and a one-dimensional nanofiber structure CeO2 loaded single-atom catalyst is obtained by loading the rhodium source) of RuCl3 solution (Rh ion concentration is 1.954 mg / mL) was added during stirring. The reaction was stirred at room temperature for 6 h, and finally dried in an oven at 60°C for 12 h. Under hydrogen conditions, the temperature was raised from room temperature to 400°C at a rate of 2°C / min, kept constant for 3 h, and finally cooled to room temperature at a rate of 10°C / min to obtain a single-atom Rh-CeO2-50 catalyst.

[0072] Comparative Example 1

[0073] A method for preparing a one-dimensional nanofiber structured CeO2-supported single-atom catalyst comprises the following steps:

[0074] (1) Preparation of CeO2-25 carrier: 8.6844 g (20 mmol) of cerium nitrate was dissolved in a mixed solvent of 25 mL of anhydrous ethanol and 75 mL of ultrapure water at room temperature to obtain a cerium nitrate solution; 4.6123 g (48 mmol) of ammonium carbonate was dissolved in a mixed solvent of 25 mL of anhydrous ethanol and 75 mL of ultrapure water to obtain an ammonium carbonate solution; the ammonium carbonate solution was poured into the cerium nitrate solution under stirring, and the mixture was stirred at room temperature for 12 h. The solid precipitate was collected by filtration, washed three times with deionized water, dried at 60°C for 12 h, and then heated from room temperature to 500°C at a rate of 2°C / min under air conditions and kept at this temperature for 4 h to obtain a light yellow powder, which is the CeO2-25 carrier;

[0075] (2) Preparation of Rh-CeO2-25 catalyst: 0.5 g of the CeO2-25 carrier prepared in step (1) was ultrasonically dispersed in 30 mL of anhydrous ethanol, and 0.25 wt% of RuCl3 solution (Rh ion concentration was 1.954 mg / mL) was added during stirring. The reaction was stirred at room temperature for 6 h, and finally dried in an oven at 60°C for 12 h. Under hydrogen conditions, the temperature was raised from room temperature to 400°C at a rate of 2°C / min, kept constant for 3 h, and finally cooled to room temperature at a rate of 10°C / min to obtain a single-atom Rh-CeO2-25 catalyst.

[0076] Comparative Example 2

[0077] A method for preparing a one-dimensional nanofiber structured CeO2-supported single-atom catalyst comprises the following steps:

[0078] (1) Preparation of CeO2-75 carrier: 8.6844 g (20 mmol) of cerium nitrate was dissolved in a mixed solvent of 75 mL of anhydrous ethanol and 25 mL of ultrapure water at room temperature to obtain a cerium nitrate solution; 4.6123 g (48 mmol) of ammonium carbonate was dissolved in a mixed solvent of 75 mL of anhydrous ethanol and 25 mL of ultrapure water to obtain an ammonium carbonate solution; the ammonium carbonate solution was poured into the cerium nitrate solution under stirring, and the mixture was stirred at room temperature for 12 h. The solid precipitate was collected by filtration, washed three times with deionized water, dried at 60°C for 12 h, and then heated from room temperature to 500°C at a rate of 2°C / min under air conditions and kept at this temperature for 4 h to obtain a light yellow powder, which is the CeO2-75 carrier;

[0079] (2) Preparation of Rh-CeO2-75 catalyst: 0.5 g of the CeO2-75 carrier prepared in step (1) was ultrasonically dispersed in 30 mL of anhydrous ethanol, and 0.25 wt% of RuCl3 solution (Rh ion concentration was 1.954 mg / mL) was added during stirring. The reaction was stirred at room temperature for 6 h, and finally dried in an oven at 60°C for 12 h. Under hydrogen conditions, the temperature was raised from room temperature to 400°C at a rate of 2°C / min, kept constant for 3 h, and finally cooled to room temperature at a rate of 10°C / min to obtain a single-atom Rh-CeO2-75 catalyst.

[0080] Figure 1 This is the SEM image of the CeO2-50 carrier prepared in Example 1. Figure 1 As can be seen in the figure, the CeO2-50 carrier exhibits a uniform nanofiber structure. This indicates that when the ratio of anhydrous ethanol to ultrapure water is 50:50, the CeO2 nanofiber structure is more regular and uniform, indicating that the solvent ratio has a significant impact on the morphology of nanofibers, and this ratio is conducive to the formation of uniform, complete, and high-quality one-dimensional nanofiber structures.

[0081] Figure 2 The SEM images (5 μm and 1 μm) of the CeO2-25 carrier prepared in Comparative Example 1 are shown in FIG. Figure 2 As can be seen in the figure, the CeO2-25 support gradually develops a nanofiber structure. This indicates that during the preparation process, by controlling the solvent ratio (anhydrous ethanol to ultrapure water ratio of 25:75), CeO2 can be induced to form a preliminary nanofiber structure, but the fiber morphology is not yet completely uniform and regular.

[0082] Figure 3 The SEM image of the CeO2-75 carrier prepared in Comparative Example 2 is shown in FIG. Figure 3 As can be seen in the CeO2-75 support, the nanofibers become shorter and thicker. This indicates that when the ratio of anhydrous ethanol to ultrapure water is further increased to 75:25, the nanofiber morphology changes, becoming shorter and thicker. This may be because the change in solvent ratio affects the growth direction and rate of CeO2, resulting in increased heterogeneity in the fiber structure.

[0083] Figure 4 TEM image of Rh-CeO2-50 prepared in Example 1; Figure 4 In the Rh-CeO2-50 catalyst, it can be observed that rhodium (Rh) is highly dispersed in the form of single atoms on the CeO2 nanofiber support. This indicates that during the preparation process, the rhodium source is successfully loaded on the CeO2 nanofibers in the form of single atoms and is evenly dispersed, which is crucial for improving the activity and stability of the catalyst.

[0084] Figure 5 The XRD patterns of CeO2-25, CeO2-50, and CeO2-75 supports show the crystal structure of CeO2 supports at different solvent ratios. According to literature, the XRD patterns of CeO2 supports indicate the cubic fluorite structure of the CeO2 crystal phase (JCPDS34-0394), and no characteristic peaks of other impurities are found in the patterns, confirming the purity of CeO2. Further comparison revealed that the diffraction peak intensity of CeO2-50 is higher, further confirming the influence of solvent ratio on CeO2 crystallinity, with CeO2-50 exhibiting a more ideal crystalline structure.

[0085] Application Example 1

[0086] The photothermal catalytic performance of the catalysts prepared in Example 1 and Comparative Examples 1-2 was tested by using a PLS-SXE300 xenon lamp as the light source for the reaction to simulate sunlight with a light intensity of 44.60 mW / cm 2The light is focused by a Fresnel lens into a spot with a diameter of about 2 cm. The reaction gas is a mixture of CO2:H2:N2=10%:40%:50% (volume ratio). The reaction flow rate is 20 mL / min. The conversion rate of carbon dioxide to methane catalyzed by the obtained catalyst (temperature range is 320-350°C) is as follows: Figure 6 shown.

[0087] Figure 6 The photothermal catalytic performance diagram of single-atom Rh-CeO2-25 catalyst, single-atom Rh-CeO2-50 catalyst and single-atom Rh-CeO2-75 catalyst. Figure 6 As can be seen in the photothermal catalytic carbon dioxide methanation reaction, the single-atom Rh-CeO2-50 catalyst has the highest conversion rate. This indicates that the nanofibrous structure of the CeO2-50 support and the loaded single-atom rhodium have the best synergistic effect in this catalytic reaction, which can efficiently promote the methanation reaction of carbon dioxide.

[0088] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a one-dimensional nanofiber structure CeO2-supported single-atom catalyst, characterized in that: The following steps are involved: (1) dissolving a cerium source in a mixed solvent of ultrapure water and anhydrous ethanol to obtain a solution A; dissolving a precipitant in a mixed solvent of ultrapure water and anhydrous ethanol to obtain a solution B; pouring the solution B into the solution A under stirring, reacting with stirring, filtering, washing, drying and calcining to obtain a CeO2 carrier; (2) The CeO2 carrier is dispersed in anhydrous ethanol, a rhodium source is added during stirring, the reaction is stirred at room temperature, and then dried and calcined to obtain a one-dimensional nanofiber structure CeO2 supported single atom catalyst.

2. The method for preparing a one-dimensional nanofiber structure CeO2-supported single-atom catalyst according to claim 1, characterized in that: When preparing solution A, the ratio of the cerium source to the mixed solvent is (5-10) g:100 mL, wherein the volume ratio of the ultrapure water to anhydrous ethanol is 1:1; When preparing solution B, the usage ratio of the precipitant to the mixed solvent is (4-5) g:100 mL, wherein the volume ratio of the ultrapure water to anhydrous ethanol is 1:

1.

3. The method for preparing a one-dimensional nanofiber structure CeO2-supported single-atom catalyst according to claim 2, characterized in that: The cerium source is cerium nitrate or cerium acetate; and the precipitant is ammonium carbonate or ammonium bicarbonate.

4. The method for preparing a one-dimensional nanofiber structure CeO2-supported single-atom catalyst according to claim 1, characterized in that: In step (1), the stirring reaction time is 12 hours.

5. The method for preparing a one-dimensional nanofiber structure CeO2-supported single-atom catalyst according to claim 1, characterized in that: In step (2), the usage ratio of the CeO2 carrier to anhydrous ethanol is (0.1-10) g: (20-100) mL.

6. The method for preparing a one-dimensional nanofiber structure CeO2-supported single-atom catalyst according to claim 1, characterized in that: The rhodium source is one or more of rhodium chloride solution, rhodium acetate solution and rhodium nitrate solution; and the loading amount is 0.05-5wt%.

7. The method for preparing a one-dimensional nanofiber structure CeO2-supported single-atom catalyst according to claim 1, characterized in that: In step (2), the stirring reaction time at room temperature is 4-8 hours.

8. The method for preparing a one-dimensional nanofiber structure CeO2-supported single-atom catalyst according to claim 1, characterized in that: In step (1) and step (2), the specific operating steps of the calcination are: raising the temperature from room temperature to 300-800°C at a rate of 1-5°C / min, and keeping it at this temperature for 2-6 hours, wherein step (2) is carried out under a hydrogen or nitrogen atmosphere.

9. A one-dimensional nanofiber structure CeO2 supported single atom catalyst, characterized in that: The method is prepared by any one of claims 1 to 8.

10. Use of the one-dimensional nanofiber structured CeO2-supported single-atom catalyst as claimed in claim 9 in solar thermal catalytic carbon dioxide methanation.

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