A stepwise confined diatomic catalyst, a preparation method and application thereof in electrocatalytic synthesis of urea
By forming CeOx nano-islands on SiO2 and dispersing Cu and Sn atoms, a CuSn diatomic catalyst was prepared, which solved the problems of single active site and poor selectivity of the catalyst and achieved the effect of efficient electrocatalytic synthesis of urea.
Patent Information
- Application Number
- CN202411778632.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-05
- Publication Date
- 2025-11-21
- Estimated Expiration
- 2044-12-05
AI Technical Summary
Existing catalysts struggle to achieve ideal urea yield and FE in the CO2 and NO3- co-reduction synthesis of urea system, exhibiting problems such as single catalytic active sites, poor selectivity, and low activity.
By employing a stepwise confined CuSn diatomic catalyst, Cu and Sn atoms are uniformly dispersed on high specific surface area gas-phase SiO2 to form CeOx nanocolloids, thereby creating dual active sites that synergistically activate C and N substrates, suppress unfavorable reactions, and improve selectivity.
It achieves high urea yields of 24–56 mmol h⁻¹ gcat⁻¹ and stable catalytic performance. The catalyst is easy to recover and reuse, maintaining its activity.
Smart Images
Figure CN119332295B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of heterogeneous catalyst preparation and electrocatalytic synthesis of urea, and in particular to a stepwise confined diatomic catalyst, its preparation method, and its application in the electrocatalytic synthesis of urea. Background Technology
[0002] Human dependence on fossil fuels has increased significantly, raising widespread global concerns about energy security, the environment, and the economy. Recent studies have found that CO2 and NO3 are major greenhouse gases. - Electrocatalytic conversion technology using wastewater pollutants as raw materials can effectively synthesize urea, an important chemical nitrogen fertilizer. It is worth noting that urea, as a major industrial product, has adapted to the rapid development of the world's population by supporting the rapid development of agricultural production. However, traditional industrial urea production uses CO2 and NH3 under harsh conditions of high temperature and high pressure. The acquisition of NH3 relies on the Haber-Bosch process, which further causes environmental pollution and consumes a huge amount of energy. Based on the evaluation of the ease of obtaining raw materials and energy consumption, a technology using NO2 to produce urea is being developed. 3- The application of electrocatalytic synthesis technology, driven by renewable electricity and replacing the difficult-to-obtain NH3, to urea synthesis is of great significance for reforming the urea industry. It also reduces water pollution and maximizes the utilization of waste resources.
[0003] Currently, in CO2 and NO 3- In the co-reduction synthesis of urea, the formation of multiple carbon- and nitrogen-containing reduction products and the occurrence of a competitive hydrogen evolution reaction (HER) make it difficult to achieve ideal urea yield and FE. Based on previous reports, to achieve a double harvest of urea yield and FE, the following challenges need to be overcome: 1) The catalyst must be able to simultaneously satisfy the co-activation and reduction of C and N substrates; 2) Optimize the adsorption energies of key C and N intermediates; 3) Suppress the occurrence of competitive reactions that are unfavorable to urea formation and avoid complex product distributions; 4) Construct highly selective multi-active sites suitable for the reduction of different substrates and the formation of CN-coupled precursors; 5) The CN coupling process must be thermodynamically and kinetically feasible. Therefore, it is crucial to actively develop catalysts with strong CO2 and NO... 3- Electrocatalysts, which possess both reducing power and the ability to selectively form intermediates that facilitate the synthesis of urea, have become crucial for overcoming numerous challenges.
[0004] Among numerous catalytic materials, atomically dispersed catalysts represent a significant advancement in the field of catalysis in recent years, particularly demonstrating remarkable potential and advantages in electrocatalytic reactions. Traditional catalysts are often nanoparticles composed of multiple metal atoms, while atomically dispersed catalysts highly disperse individual metal atoms on a support, forming single-atom sites. This structure possesses unique catalytic properties and reaction selectivity. However, current single-component atomically dispersed catalysts suffer from limitations such as a single active site, poor selectivity, and low catalytic activity. Therefore, there is an urgent need to provide a diatomic catalyst with dual active sites to overcome the shortcomings of existing technologies. Summary of the Invention
[0005] Based on the above, this invention provides a stepwise confined diatomic catalyst, its preparation method, and its application in the electrocatalytic synthesis of urea. The stepwise confined CuSn diatomic catalyst provided by this invention overcomes the shortcomings of primary dispersed catalysts, such as poor dispersion, easy aggregation, and single active site.
[0006] To achieve the above objectives, the present invention provides the following solution:
[0007] One of the technical solutions of this invention is a method for preparing a stepwise confined diatom catalyst, comprising the following steps:
[0008] Step 1: Disperse gaseous SiO2 in water and add Ce precursor to obtain a mixed solution;
[0009] An alkaline solution is added to the mixed solution to initiate a reaction, and the resulting precipitate is calcined to obtain CeO. x @SiO2;
[0010] Step 2, CeO x SiO2 is added to water, followed by the addition of Cu and Sn salts, and then Na2CO3 solution is added for deposition. The deposited solid is calcined and activated to obtain the stepwise confined diatomic catalyst (CuSn / CeO2). x @SiO2).
[0011] The second technical solution of the present invention is a stepwise confined diatomic catalyst prepared according to the above preparation method.
[0012] The third technical solution of the present invention is an electrode material, which is prepared by combining the above-mentioned stepwise confined diatomic catalyst with a matrix material.
[0013] The fourth technical solution of this invention refers to the above-mentioned stepwise confined diatomic catalyst or the above-mentioned electrode material in the electrocatalysis of CO2 and NO3. - Applications in the synthesis of urea.
[0014] The fifth technical solution of this invention: an electrocatalytic method for reacting CO2 and NO. 3- The method for synthesizing urea involves using the aforementioned electrode material as the working electrode in a container containing NO3. - Urea is generated in a CO2-saturated electrolyte via CN coupling.
[0015] The present invention discloses the following technical effects:
[0016] 1. This invention uses abundant, high-specific-surface-area gaseous SiO2 as a matrix, and employs a simple electrostatic adsorption method to adsorb ultra-small CeO2. x Nano-colloid islands grafted onto SiO2. Uniformly dispersed CeO2. x As an atomic support, Cu and Sn atoms are confined to the island, avoiding problems such as the easy aggregation of atomically dispersed catalysts at high temperatures and the difficulty in fully exposing active sites.
[0017] 2. The CuSn diatomic catalyst prepared in this invention was used to catalyze the urea synthesis reaction, exhibiting a yield of 24–56 mmol / L. -1 g cat -1 The range of higher urea yields.
[0018] 3. The catalyst prepared by this invention is heterogeneous, easy to recover after the catalytic reaction, and still maintains stable activity after being reused 9 times. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 The images show X-ray diffraction patterns of the composite supports and catalyst samples prepared in Examples 1-4 of this invention; where a is the composite support prepared in Example 1 and b is the catalyst prepared in Examples 2-3.
[0021] Figure 2 The images show the Raman spectra of the composite support and catalyst samples prepared in Examples 1-4 of this invention.
[0022] Figure 3 A high-angle annular dark-field scanning transmission electron microscope image of the composite carrier prepared in Embodiment 1 of the present invention.
[0023] Figure 4 This is an elemental mapping image of the catalyst prepared in Embodiment 4 of the present invention.
[0024] Figure 5 The extended X-ray absorption spectrum of the catalyst prepared in Embodiment 4 of this invention is shown; where a is CuSn / CeO x @Extended X-ray absorption fine structure spectrum of Cu K-edge in SiO2, b is CuSn / CeO x Extended X-ray absorption fine structure spectrum of Sn K-edge in SiO2.
[0025] Figure 6 The composite support and catalyst samples prepared in Examples 1-4 of this invention exhibit catalytic performance in urea synthesis at partial application potentials; where a represents CeO₂. x @SiO2 urea yield rate and urea Faraday efficiency at different application potentials urea The distribution of ), where b is Sn / CeO x @The urea yield and FEurea distribution of SiO2 at different application potentials, where c is the Cu / CeO x @The urea yield and FEurea distribution of SiO2 at different application potentials, where d represents CuSn / CeO x @SiO2 urea yield and FEurea distribution at different application potentials.
[0026] Figure 7 The stability test results of the catalyst sample prepared in Example 4 of this invention at -0.7V for electrocatalytic urea synthesis are shown in the figure. Detailed Implementation
[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.
[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.
[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.
[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.
[0032] In this invention, the diatomic catalyst has two different metal atom active sites. One metal (Cu) provides excellent catalytic activity, while the other metal (Sn) modulates the structure and stability of the reaction intermediate, thereby improving the selectivity of the reaction. This synergistic effect enables the diatomic catalyst to significantly improve the reaction rate and product selectivity in electrocatalytic reactions, and it is particularly suitable for CN coupling reactions involving the reduction of two substrates.
[0033] This invention uses high specific surface area gaseous SiO2 as the substrate material. Under alkaline conditions, a Ce precursor (Ce(NO3)3·6H2O) is formed on the SiO2 surface as a precipitate with an electrostatic adsorption layer. Subsequently, under high-temperature calcination, CeO3 with ultra-small size grafted onto the SiO2 substrate is formed. x Nano-colloid islands; CeO x The defects contained within the material serve as anchoring points to support Cu and Sn atoms, allowing for the synthesis of CuSn / CeO through recalcination. x @SiO2 diatomic catalyst.
[0034] The first aspect of this invention provides a method for preparing a stepwise confined diatomic catalyst, comprising the following steps:
[0035] Step 1: Disperse gaseous SiO2 in water and add Ce precursor to obtain a mixed solution;
[0036] An alkaline solution is added to the mixed solution to initiate a reaction, and the resulting precipitate is calcined to obtain CeO. x @SiO2;
[0037] Step 2, CeO x SiO2 is added to water, followed by the addition of Cu and Sn salts, and then Na2CO3 solution is added for deposition. The deposited solid is calcined and activated to obtain the stepwise confined diatomic catalyst (CuSn / CeO2). x @SiO2).
[0038] In a preferred embodiment of the present invention, the molar ratio of the gaseous SiO2 to the Ce precursor is (6.0-15.0):(0.4-1.0). When the Ce precursor content is too high, it will lead to the formation of CeO2. x The nanoclusters are unevenly distributed or too large in size; when the Ce precursor content is too low, it will lead to CeO x It is difficult to form clusters or the cluster size is too small, which is not conducive to atomic loading; the Ce precursor is Ce(NO3)3·6H2O.
[0039] In a preferred embodiment of the present invention, the alkaline solution is ammonia water; the amount of alkaline solution added is such that the pH of the reaction system is 8-9.
[0040] In a preferred embodiment of the present invention, in step 1, the reaction time is 2-5 min; the calcination temperature is 450-550℃ and the time is 10-24 h.
[0041] Step 1 further includes filtering out the precipitate and washing and drying it after the reaction is completed.
[0042] In a preferred embodiment of the present invention, the mass ratio of CeOx@SiO2 to the Cu salt and Sn salt is (0.1-0.2):(0.01-0.125):(0.005-0.1); the Cu salt is CuCl2; and the Sn salt is SnCl4.
[0043] In a preferred embodiment of the present invention, the Cu salt and Sn salt are added to the reaction system in solution form. In some specific embodiments of the present invention, the concentration of the Cu salt solution is 50 mg / mL. -1 The concentration of the Sn salt solution is 50 mg / mL. -1 .
[0044] In a preferred embodiment of the present invention, in step 2, the mass ratio of Na2CO3 to Cu salt and Sn salt in the Na2CO3 solution is (0.65-2):(0.01-0.125):(0.005-0.1); the concentration of the Na2CO3 solution is 50 mg / mL. -1The deposition time is 4-6 hours; the calcination temperature is 550-650℃ and the time is 12 hours; the activation temperature is 250-350℃ and the time is 1 hour. Step 2 further includes filtering out the solid, washing, and drying it after deposition.
[0045] The concentrations of Cu salt solution, Sn salt solution, and Na2CO3 solution in this invention are merely exemplary. This invention does not impose any particular limitation on the concentrations of Cu salt solution, Sn salt solution, and Na2CO3 solution, as long as the mass ratio of Na2CO3 to Cu salt and Sn salt is (0.65-2):(0.01-0.125):(0.005-0.1).
[0046] In this invention, Na2CO3 serves to deposit Cu and Sn in the solution.
[0047] A second aspect of the present invention provides a stepwise confined diatomic catalyst (CuSn / CeO) prepared according to the above-described preparation method. x @SiO2).
[0048] CuSn / CeO prepared by this invention x Cu and Sn atoms loaded on SiO2 are isolated from each other between the islands. x The contents of Cu and Sn atoms in SiO2 are 0.2–3.0 wt% and 0.2–2.5 wt%, respectively.
[0049] CeO x In @SiO2, the value of x ranges from 3 to 4.
[0050] A third aspect of the present invention provides an electrode material prepared by combining the above-described stepwise confined diatomic catalyst with a matrix material.
[0051] This invention does not impose any particular limitation on the type of substrate material; any substrate material well-known to those skilled in the art that can be used to prepare electrode materials may be used. In some embodiments of this invention, the substrate material is carbon paper.
[0052] The fourth aspect of this invention provides the above-described stepwise confined diatomic catalyst or the above-described electrode material for the electrocatalysis of CO2 and NO3. - Applications in the synthesis of urea.
[0053] The fifth aspect of the present invention provides an electrocatalytic reaction of CO2 and NO. 3- The method for synthesizing urea involves using the aforementioned electrode material as the working electrode in a container containing NO3. - Urea is generated in a CO2-saturated electrolyte via CN coupling.
[0054] In some embodiments of the present invention, the urea yield ranges from 24 to 56 mmol / h. -1 g cat -1 .
[0055] In some specific embodiments of the present invention, the above-mentioned CuSn / CeO x Electrode material was prepared by ultrasonically mixing SiO2 with isopropanol, 5wt% naphthol solution and deionized water, and then reacted in a KNO3 electrolyte solution saturated with CO2 to synthesize urea.
[0056] CuSn / CeO on the electrode material x The loading of SiO2 was 0.1–0.2 mg / cm³. -2 .
[0057] The reaction for synthesizing urea is carried out at room temperature for 0.5 to 2 hours.
[0058] The reaction uses an H-type electrolytic cell as the reactor, with AgCl / Ag as the reference electrode, Pt foil as the counter electrode, and the aforementioned electrode materials as the working electrode.
[0059] After the reaction is completed, the catalyst-loaded electrode is directly removed, repeatedly soaked and washed with deionized water several times, and then naturally dried before being used again for electrocatalytic synthesis of urea.
[0060] Unless otherwise specified, all solutions used in the specific embodiments of this invention are water-based solvents.
[0061] The method of this invention first uses electrostatic adsorption to remove CeO x CeO is obtained by grafting onto SiO2 and calcining at high temperature. x A SiO2 composite support was then formed. Cu and Sn atoms were introduced onto the support surface, and after high-temperature calcination, a CuSn diatomic catalyst was finally formed. The highly active atoms separated by islands efficiently capture and activate C and N species. Using a CO2-saturated KNO3 solution as the electrolyte, the catalyst was used for the electrocatalytic synthesis of urea at different application potentials, exhibiting good catalytic performance and Faraday efficiency.
[0062] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.
[0063] The Nafion used in this embodiment of the invention is a transparent liquid of DuPont brand, model D520, with volatile organic compound content of 50+3%, exchange capacity of 1.03-1.12, and resin solid content of 5%.
[0064] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0065] Example 1
[0066] 1. Composite support with stepwise confinement effect (CeO) x Preparation of SiO2 (composite support)
[0067] (1) Disperse 0.72g of gaseous SiO2 in 200mL of deionized water and sonicate for about 30min. Add 0.8mmol Ce(NO3)3·6H2O under vigorous stirring.
[0068] (2) After the solid has completely dissolved, quickly add 1.6 mL of 2 mol L. -1 The NH3·H2O was added (the pH of the reaction system was 8.7 at this point). After reacting for 3 minutes, the precipitate was filtered out and washed with deionized water until neutral. The resulting gelatinous solid was dried naturally at room temperature and then calcined at 500℃ for 12 hours to obtain CeOx@SiO2.
[0069] 2. Catalytic activity test
[0070] 2mg CeO x The catalyst ink was prepared by ultrasonically mixing SiO2 in 635 μL isopropanol, 315 μL deionized water, and 50 μL 5 wt% naphthol solution for 40 min. 50 μL of the catalyst ink was drop-coated onto 1×1 cm carbon paper and dried to serve as the working electrode. Electrolysis was performed for 0.5 h at room temperature in a CO2-saturated 0.1 M KNO3 solution using a chronoamperometry method (-0.5 V to -1.0 V), with a CO2 flow rate of 30 mL / min. -1 .
[0071] The urea content was calculated using the urease decomposition method, and the urea production rate was found to be 3.2 mmol / h. - 1 g cat -1 .
[0072] Example 2
[0073] 1. Stepwise confinement of Sn single-atom catalysts (Sn / CeO) x Preparation of SiO2 (catalyst)
[0074] (1) 0.129g of CeO prepared in Example 1 was used. x @SiO2 and 10 mL of deionized water were ultrasonically mixed for 30 min, and then 1 mL of 50 mg / mL solution was added dropwise at 600 rpm. -1SnCl4 solution, after stirring evenly, add 13 mL of 50 mg / mL solution. -1 Na₂CO₃ was deposited for 5 hours. The solid sample was filtered out, washed with deionized water, and then air-dried at room temperature.
[0075] (2) After obtaining the solid sample, it was first calcined at 600℃ for 12h, and then activated at 300℃ for 1h in a hydrogen atmosphere; thus, a Sn single-atom catalyst with stepwise confinement was obtained.
[0076] 2. Catalytic activity test
[0077] The catalytic activity test was the same as in Example 1, except that CeO2 was used instead of CeO2. x @SiO2 replaced with Sn / CeO x @SiO2. The results showed that the urea formation rate was 11.81 mmol / h. -1 g cat -1 .
[0078] Example 3
[0079] 1. Stepwise confinement of Cu single-atom catalysts (Cu / CeO) x Preparation of SiO2 (catalyst)
[0080] (1) 0.129g of CeO prepared in Example 1 was used. x @SiO2 and 10 mL of deionized water were ultrasonically mixed for 30 min, and then 2 mL of 50 mg / mL solution was added dropwise at 600 rpm. -1 After mixing the CuCl2 solution thoroughly, add 13 mL of 50 mg / mL CuCl2 solution. -1 Na₂CO₃ was deposited for 5 hours. The solid sample was filtered out, washed with deionized water, and then air-dried at room temperature.
[0081] (2) The solid sample was first calcined at 600℃ for 12 h, and then activated at 300℃ for 1 h under a hydrogen atmosphere; a stepwise confined Cu single-atom catalyst was obtained. (That is, the catalyst preparation conditions are exactly the same as in Example 2, except that 1 mL of 50 mg / mL catalyst was added in the preparation method.) -1 The SnCl4 solution was changed to 2 mL of 50 mg / mL solution. -1 CuCl2 solution)
[0082] 2. Catalytic activity test
[0083] The catalytic activity test was the same as in Example 1, except that CeO2 was used instead of CeO2. x @SiO2 replaced with Cu / CeO x @SiO2. The results showed that the urea formation rate was 35.69 mmol / h. -1 gcat -1 .
[0084] Example 4
[0085] 1. Stepwise confinement of CuSn diatomic catalysts (CuSn / CeO) x Preparation of SiO2 (catalyst)
[0086] (1) 0.129g of CeO prepared in Example 1 was used. x @SiO2 and 10 mL of deionized water were ultrasonically mixed for 30 min, and then 1 mL of 50 mg / mL solution was added dropwise at 600 rpm. -1 SnCl4 solution and 2 mL 50 mg mL -1 After mixing the CuCl2 solution thoroughly, add 13 mL of 50 mg / mL CuCl2 solution. -1 Na2CO3 deposition for 5 hours. The solid sample was filtered out, washed with deionized water, and then air-dried at room temperature.
[0087] (2) The solid sample was first calcined at 600℃ for 12 h, and then activated at 300℃ for 1 h under a hydrogen atmosphere; thus, a stepwise confined Sn single-atom catalyst was obtained. (That is, the catalyst preparation conditions were exactly the same as in Example 2, except that 1 mL of 50 mg / mL catalyst was added to the preparation method.) -1 Along with the SnCl4 solution, 2 mL of 50 mg / mL solution was also added. -1 CuCl2 solution)
[0088] 2. Catalytic activity test
[0089] The catalytic activity test was the same as in Example 1, except that CeO2 was used instead of CeO2. x @SiO2 replaced with CuSn / CeO x The SiO2 results indicate that the urea formation rate is 55.81 mmol / h. -1 g cat. -1 .
[0090] X-ray diffraction spectroscopy was performed on the composite support and catalyst samples obtained in Examples 1-4, and the results are as follows: Figure 1 As shown, this invention successfully prepared CeO with a stepwise confinement effect. x In the SiO2 composite support, the Sn, Cu single atoms and CuSn diatoms placed on the composite support did not agglomerate.
[0091] Raman spectroscopy was performed on the composite support and catalyst samples obtained in Examples 1-4, and the results are as follows: Figure 2 As shown, the present invention uses CeO xWhen combined with SiO2, the catalyst undergoes lattice distortion and generates abundant oxygen vacancy defects.
[0092] Figure 3 This is a high-angle annular dark-field scanning transmission electron microscope image of the composite carrier obtained in Example 1, from... Figure 3 It can be seen that CeO is uniformly loaded on the surface of SiO2. x Nano-colloid islands.
[0093] Figure 4 The image shows the elemental mapping of the CuSn diatomic catalyst with stepwise confinement obtained in Example 4, demonstrating the uniform dispersion of Cu and Sn.
[0094] Figure 5 To study the local coordination environment of Cu and Sn atoms in the CuSn diatomic catalyst with stepwise confinement prepared in Example 4, an extended X-ray absorption spectrum was obtained, proving that it has a diatomic structure.
[0095] Figure 6 The electrocatalytic synthesis of urea by the composite support and catalyst samples obtained in Examples 1-4 demonstrates that the CuSn diatomic catalyst has relatively ideal catalytic performance.
[0096] Figure 7 The stability test of the sample obtained in Example 4 during the urea synthesis reaction at an application potential of -0.7V demonstrated that the CuSn diatomic catalyst has relatively good stability.
[0097] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for preparing a stepwise confined diatomic catalyst, characterized in that, Includes the following steps: Step 1: Disperse gaseous SiO2 in water and add Ce precursor to obtain a mixed solution; add alkaline solution to the mixed solution to carry out the reaction, and calcine the resulting precipitate to obtain CeO. x @SiO2; Step 2, CeO x SiO2 was added to water, followed by the addition of Cu and Sn salts, and then Na2CO3 solution was added for deposition. The deposited solid was calcined and then activated under a hydrogen atmosphere to obtain the stepwise confined diatomic catalyst CuSn / CeO2. x @SiO2; The molar ratio of gaseous SiO2 to the Ce precursor is (6.0-15.0):(0.4-1.0). The CeO x The mass ratio of SiO2 to the Cu and Sn salts is (0.1-0.2):(0.01-0.125):(0.005-0.1). In step 2, the mass ratio of Na2CO3 in the Na2CO3 solution to the Cu salt and Sn salt is (0.65-2):(0.01-0.125):(0.005-0.1); the calcination temperature is 550-650 ℃; and the activation temperature is 250-350 ℃.
2. The method for preparing a stepwise confined diatom catalyst according to claim 1, characterized in that, The Ce precursor is Ce(NO3)3·6H2O.
3. The method for preparing a stepwise confined diatom catalyst according to claim 1, characterized in that, The alkaline solution is ammonia water; the amount of alkaline solution added is sufficient to make the pH of the reaction system 8-9.
4. The method for preparing a stepwise confined diatom catalyst according to claim 1, characterized in that, In step 1, the reaction time is 2-5 min; the calcination temperature is 450-550 ℃ and the time is 10-24 h.
5. The method for preparing a stepwise confined diatom catalyst according to claim 1, characterized in that, The Cu salt is CuCl2; the Sn salt is SnCl4.
6. The method for preparing a stepwise confined diatom catalyst according to claim 1, characterized in that, In step 2, the deposition time is 4-6 h; the calcination time is 12 h; and the activation time is 1 h.
7. The stepwise confined diatomic catalyst CuSn / CeO prepared by the preparation method according to any one of claims 1-6 x @SiO2.
8. An electrode material, characterized in that, By using the stepwise confinement of the diatomic catalyst CuSn / CeO as described in claim 7 x It is prepared by combining SiO2 with a matrix material.
9. The stepwise confinement diatomic catalyst CuSn / CeO as described in claim 7 x @SiO2 or the electrode material according to claim 8 in the electrocatalysis of CO2 and NO3 - Applications in the synthesis of urea.
10. An electrocatalytic method for reacting CO2 and NO3 - The method for synthesizing urea is characterized by, The electrode material described in claim 8 is used as the working electrode in a container containing NO3. - Urea is generated in a CO2-saturated electrolyte via CN coupling.