Supported Ag / lanthanide oxide nanocomposite and application thereof

Abstract

The invention discloses a supported Ag / lanthanide oxide nano composite material and application thereof. The preparation method comprises the following steps: firstly, obtaining a composite phase precursor through sol-gel reaction, and then calcining at high temperature to obtain a product. Mixing with conductive carbon black and the like to prepare ink slurry, dispensing the ink slurry on a carrier to prepare an electrode, and further applying the electrode to an electrochemical carbon dioxide reduction reaction. In the initial stage of the reduction reaction, the partially doped silver is rapidly separated out to the surface of the carrier oxide in situ, which indicates that abundant interfaces and oxygen defects are formed by mutual connection. The structures promote the formation of a large number of active sites, and are favorable for converting carbon dioxide into carbon monoxide. The prepared material has the carbon monoxide preparation Faraday efficiency close to 98%, the consumption of precious metal silver is greatly reduced, the synthesis method is simple, wide applicability and expansibility are achieved, certain industrial value is achieved, and current climate and environment problems are expected to be relieved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic carbon dioxide reduction catalysts, and particularly to a supported Ag / lanthanide oxide composite electrocatalyst, a preparation method thereof, and an application thereof in electrocatalytic carbon dioxide reduction. Background Art

[0002] In recent decades, due to the large consumption of non-renewable fossil fuels (such as coal, oil, etc.), a series of serious problems such as energy crisis and environmental pollution have been triggered, and global warming has thus become the focus of extensive attention in the international community. [1] To effectively address this challenge, scientists from various countries have actively carried out research and proposed a variety of innovative technologies to capture, store, and convert carbon dioxide in the atmosphere. [2] Among these technologies, using the electricity generated by renewable clean energy (including solar energy, wind energy, and tidal energy, etc.) to reduce carbon dioxide molecules into fossil fuels and high-value chemicals such as carbon monoxide, methane, ethylene, or ethanol has become one of the current highly regarded technical paths. [3] This technical solution not only helps to reduce the concentration of carbon dioxide in the atmosphere, thereby alleviating the environmental crisis, but also can convert intermittent and regional clean energy into storable chemical energy, and then produce high-value products, achieving double benefits of environmental protection and economic benefits. However, due to the chemical inertness of carbon dioxide molecules and the existence of problems such as the cathodic hydrogen evolution side reaction, the conversion efficiency of the electrochemical process is limited to a certain extent. [4] Therefore, exploring and developing electrocatalysts with simple preparation, wide applicability, and excellent performance has become an essential way to achieve large-scale commercial applications in the future.

[0003] Among the many reported catalyst types, silver-based metal materials have received extensive attention from researchers because of their high selectivity in electrochemically reducing carbon dioxide to carbon monoxide. For example, the Salehi-khojin team first experimentally studied the effect of changes in the size of silver nanoparticles on their electrocatalytic reduction performance and successfully prepared silver nanoparticles with a diameter range between 1 - 200 nm. [5] The research results show that the catalytic activity of these particles for carbon dioxide reduction shows a volcano-shaped variation law with the decrease in particle diameter. Liu et al. prepared triangular silver nanoparticles (Tri-Ag-NPs) by a direct chemical reduction method and compared them with bulk silver nanoparticles (SS-Ag-NPs) of the same size, and found that the Faraday efficiency and energy conversion effect of Tri-Ag-NPs were both significantly improved, which explained the close relationship between catalyst performance and the microscopic morphology of the material. [6]In addition to studying the size and morphology of catalysts, researchers have also focused on the effects of catalyst supports and interfaces on catalytic performance. For example, the Bao research group conducted a preliminary study on the application of the Au / Ag-ceria interface in the electrochemical carbon dioxide reduction process. Density functional theory calculations showed that interfacial catalysis is the main active site in the carbon dioxide catalytic reaction. [7] Therefore, how to obtain low-loading, highly active catalytic materials through simpler preparation processes, further clarify the reasons for the performance changes of these materials in the electrochemical carbon dioxide reduction reaction, and expand their application scope still require our in-depth exploration and discovery.

[0004] References

[0005] [1] Fei L, Sun H, Xu X, et al. Understanding the bifunctional catalytic ability of electrocatalysts for oxygen evolution reaction and urea oxidation Reaction: Recent advances and perspectives [J]. Chemical Engineering Journal, 2023: 144660.

[0006] [2] Tan K B, Xu K, Cai D, et al. Rational design of bifunctional catalysts with proper integration manners for CO and CO 2 hydrogenation into value-added products: A review [J]. Chemical Engineering Journal, 2023, 463: 142262.

[0007] [3] Seh Z W, Kibsgaard J, Dickens C F, et al. Combining theory and experiment in electrocatalysis: Insights into materials design [J]. Science, 2017, 355(6321): eaad4998.

[0008] [4] Qin Y, Zhan G, Tang C, et al. Homogeneous vacancies-enhanced orbital hybridization for selective and efficient CO 2 -to-CO electrocatalysis[J]. Nano Letters, 2023, 23(20): 9227-9234.

[0010] [5] Salehi-Khojin A, Jhong H-R M, Rosen B A, et al. Nanoparticle silver catalysts that show enhanced activity for carbon dioxide electrolysis[J]. The Journal of Physical Chemistry C, 2013, 117(4): 1627-1632.

[0011] [6] Liu S, Tao H, Zeng L, et al. Shape-dependent electrocatalytic reduction of CO 2 to CO on triangular silver nanoplates[J]. Journal of the American Chemical Society, 2017, 139(6): 2160-2163.

[0013] [7] Gao D, Zhang Y, Zhou Z, et al. Enhancing CO 2 electroreduction with the metal–oxide interface[J]. Journal of the American Chemical Society, 2017, 139(16): 5652-5655. Summary of the Invention

[0014] Objective of the Invention: Aiming at the deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a supported Ag / lanthanide oxide composite electrocatalyst, its preparation method and its application in electrocatalytic carbon dioxide reduction.

[0015] Inventive Concept: The present invention proposes an in-situ reconstructed silver / lanthanide oxide nanocatalyst, which has rich interfacial characteristics and oxygen defects. The preparation method of this catalyst is simple and easy to implement, and it can efficiently synthesize carbon monoxide in the application of the cathode of carbon dioxide electroreduction.

[0016] To solve the above technical problems, the present invention discloses the following technical solutions:

[0017] In the first aspect of the present invention, provided is:

[0018] A silver / lanthanide oxide nanocomposite with a small amount of silver loaded, the preferred range of the loading amount of Ag in the composite is 20-25 wt%, and its loading amount can be precisely controlled in the synthesis step.

[0019] In some embodiments, for the composite phase catalyst, the carrier is a lanthanide oxide, which is Pr 6 O 11 、La 2 O 3 、CeO 2 and Nd 2 O 3 or any combination of several of them; the active metal is silver. In some embodiments, the molecular formula of the composite phase catalyst is Ag / Pr 6 O 11 .

[0020] In some embodiments, the composite phase catalyst is in the shape of nanospheres, and its diameter range is 50-200 nm, such as 80, 100, 120, 150, 180 nm. After in-situ reconstruction, the diameter of the preferred catalyst nanospheres is further optimized to 40-100 nm.

[0021] In some embodiments, the composite material is detected by XPS, and its oxygen defect concentration is 17.87%-19.87%. After testing the carbon dioxide electroreduction performance, its oxygen defect concentration is further increased to 21.88%-23.88%.

[0022] In the second aspect of the present invention, provided is:

[0023] The preparation method of the silver / lanthanide oxide nanocomposite catalyst described in the first aspect above includes the following steps:

[0024] (1) According to the stoichiometric ratio, dissolve lanthanide nitrate and silver nitrate in deionized water and stir evenly to obtain a clear and transparent solution;

[0025] (2) Ethylenediaminetetraacetic acid (EDTA) and citric acid monohydrate (CA) are added as metal ion complexing agents to the obtained solution, ammonia water is added to adjust the pH to 6.5 - 7.5, and the solution is heated and stirred until it becomes gel-like;

[0026] (3) The obtained gel is dried in an oven to obtain a precursor sample, and then calcined in an air atmosphere and ground to obtain the final powder sample.

[0027] In step (1), the lanthanide nitrate is any one or a combination of several of praseodymium nitrate, lanthanum nitrate, cerium nitrate, and neodymium nitrate; the molar ratio of the lanthanide nitrate to silver nitrate is 1:1 - 4, such as 1:2, 1:3.

[0028] In step (2), the mass ratio of silver nitrate, ethylenediaminetetraacetic acid, and citric acid monohydrate is 1:5.8 - 7.8:8.9 - 10.9, such as 1:6.8:9.9.

[0029] In step (2), ammonia water is added to adjust the pH to 6.5 - 7.5, such as 7.0.

[0030] In step (3), the drying temperature is 170 - 190 °C, such as 180 °C; the drying time is 7 - 10 h, such as 8 - 9 h.

[0031] In step (3), the temperature for heating and stirring the gel-like mixture is 90 - 110 °C, such as 100 °C; the heating and drying time is 7 - 10 h.

[0032] In step (3), the calcination temperature is 500 - 900 °C, such as 700 °C; the calcination time is 1 - 3 h, such as 2 h.

[0033] In the third aspect of the present invention, provided is:

[0034] An electrode made of the silver / lanthanide oxide nanocomposite catalyst described in the first aspect above.

[0035] In some embodiments, the preparation method of the electrode is to fully mix the silver / lanthanide oxide nanocomposite catalyst with a conductive agent, a dispersant, and a binder to obtain a slurry; the obtained slurry is drop-coated on the surface of a carrier and naturally air-dried.

[0036] In some embodiments, a commercial glassy carbon electrode or a commercial carbon fiber paper is used as the carrier.

[0037] In some embodiments, the binder of the electrode is a Nafion solution or a PTFE binder.

[0038] In some embodiments, the conductive agent of the electrode is conductive carbon black.

[0039] In some embodiments, the dispersant of the negative electrode is an organic solvent, such as ethanol or isopropyl alcohol.

[0040] In some embodiments, the mass ratio of the composite material to the conductive agent is 1:0.5 - 2, such as 1:0.7 - 1.2.

[0041] In some embodiments, the dosage ratio of the composite material, the dispersant, and the binder is 10 mg:0.7 - 1.2 mL:90 - 120 μL.

[0042] In the fourth aspect of the present invention, provided is:

[0043] Application of the electrode described in the above third aspect as a cathode working electrode in the electrochemical carbon dioxide reduction reaction.

[0044] In one embodiment, the application includes the following steps:

[0045] S1: Using the above-mentioned nano-composite catalyst as the working electrode, constructing a three-electrode system and assembling it into an electrochemical cell;

[0046] S2: Passing CO 2 to saturation, applying a negative voltage, and performing the electrochemical carbon dioxide reduction reaction.

[0047] In step S1,

[0048] In some embodiments, in the three-electrode system, silver-silver chloride is used as the reference electrode, and a platinum sheet or a graphite rod is used as the counter electrode.

[0049] In step S2, in the electrochemical reaction, the reaction is carried out in an H-type electrolytic cell.

[0050] In step S2, in the electrochemical reaction, a 0.01 - 0.2 M KHCO 3 solution is used as the electrolyte, such as a 0.1 M potassium bicarbonate solution.

[0051] In the initial stage of the reduction reaction, partially doped silver is rapidly and in-situ precipitated onto the surface of the support oxide, indicating that interconnected interfaces and oxygen vacancies are formed. These structures promote the formation of a large number of active sites, which is beneficial for converting carbon dioxide into carbon monoxide. The material prepared by the present invention has a carbon monoxide Faraday efficiency of nearly 98%, greatly reducing the consumption of precious metal silver. The synthesis method is simple and has wide applicability and expandability, with certain industrial value and is expected to alleviate the current climate and environmental problems.

[0052] Beneficial effects:

[0053] The Ag-loaded oxide composite catalyst prepared by the present invention has a good crystal form and presents a black-brown powdery morphology. By introducing the doping of silver element, efficient active sites are formed between the metal and the carrier, thus significantly improving the conversion ability of the catalyst to carbon dioxide molecules. Compared with the traditional pure silver powder catalyst, the use of a small amount of silver element can not only optimize the catalytic performance but also greatly reduce the preparation cost of the catalyst.

[0054] The nano-composite electrocatalyst provided by the present invention exhibits excellent performance in catalyzing the conversion of carbon dioxide to carbon monoxide, significantly superior to the traditional silver powder catalyst. The findings on interfaces and oxygen defects in these studies provide important theoretical support for understanding the reaction mechanism of carbon dioxide electrocatalytic reduction and also open up a new path for the application prospect of reducing the carbon dioxide concentration in the atmosphere.

[0055] The low-loading silver silver / lanthanide oxide composite material involved in the present invention can be produced by processes such as the traditional sol-gel method and sodium borohydride reduction method. Its preparation process is simple and easy, and the mass ratio of silver element in the material is relatively low, greatly reducing the cost. The selection of the carrier of this catalyst is not only applicable to praseodymium oxide but can also be extended to other lanthanide oxides and transition metal oxides, having good potential for large-scale production and batch substitution manufacturing. Brief Description of the Drawings

[0056] The following further specifically describes the present invention in conjunction with the drawings and specific embodiments, and the above and / or other advantages of the present invention will become clearer.

[0057] Figure 1 is the preparation flow chart of the technical solution in the present invention.

[0058] Figure 2 is the schematic diagram of the two-phase structure of the composite catalyst prepared in Example 1 and Comparative Example 3 in the present invention.

[0059] Figure 3 is Ag / Pr 6 O 11 、Pr 6 O 11 、Ag powder and Ag+Pr 6 O 11 X-ray diffraction pattern.

[0060] Figure 4 is the X-ray diffraction pattern of Ag / La 2 O 3 、Ag / CeO 2 and Ag / Nd 2 O 3 X-ray diffraction pattern.

[0061] Figure 5 It is the Ag 3d orbital X-ray photoelectron spectrum of Example 1 described in the present invention and the sample after reaction.

[0062] Figure 6 It is the O1s orbital X-ray photoelectron spectrum of Example 1 described in the present invention, the sample after reaction, and Comparative Examples 1 and 3.

[0063] Figure 7 It is the electron paramagnetic resonance spectrum of Example 1 described in the present invention, the sample after reaction, and Comparative Examples 1 and 3.

[0064] Figure 8 It is the scanning electron microscope image and particle size distribution of Example 1 described in the present invention and the sample after reaction.

[0065] Figure 9 It is the transmission electron microscope images of Example 1 included in the present invention at different magnifications.

[0066] Figure 10 It is the normalized polarization curve graph and the graph of the relationship between the CO Faraday efficiency and voltage of the catalysts of Example 1 and Comparative Examples 1, 2, and 3 in 0.1M KHCO 3 solution.

[0067] Figure 11 It is the graph of the stability test results of the catalyst of Example 1 included in the present invention in 0.1M KHCO 3 solution.

[0068] Figure 12 It is the electrochemically active surface area graph of the catalysts of Example 1 and Comparative Examples 2 and 3 described in the present invention.

[0069] Figure 13 It is the electrochemical impedance graph of the catalysts of Example 1 and Comparative Examples 2 and 3 described in the present invention.

[0070] Figure 14 It is the graph of the relationship between the CO Faraday efficiency and voltage of Examples 2, 3, and 4 described in the present invention. Detailed implementation manners

[0071] According to the following examples, the present invention can be better understood. However, those skilled in the art can easily understand that the content described in the examples is only used to illustrate the present invention and should not and will not limit the present invention described in detail in the claims.

[0072] In the following examples, unless otherwise specified, the experimental methods are all conventional methods; unless otherwise specified, the reagents and materials can all be obtained from commercial channels.

[0073] At present, in the realization of large-scale application of electrocatalytic carbon dioxide reduction technology, it mainly faces the challenges of product selectivity change and high cost of product separation. Among many reduction products, carbon monoxide is considered to be one of the most promising products for industrialization due to its excellent selectivity and relatively easy separation process. However, the existing silver-based catalysts still need to be improved in performance, and their prices are relatively expensive. To solve these problems, the present invention proposes to modify the silver-based catalyst material to enhance its catalytic efficiency in carbon dioxide electroreduction and reduce the usage amount of silver element. Specifically, the present invention selects lanthanide oxides that do not have catalytic activity for carbon dioxide reduction as the carrier of silver element, and realizes a strong interaction between metallic silver and the carrier through a chemical synthesis method, which helps to improve the active sites of the electrocatalytic reaction. In addition, the synthesis temperature of silver / lanthanide oxide is relatively low, ranging from 500 to 900 °C, where metallic silver can form a phase at a relatively low temperature, while the formation of the oxide needs to be carried out above 500 °C. At the same time, the degree of interaction between the metal and the oxide can be controlled by adjusting the calcination temperature. Although high temperature (above 900 °C) will cause the loss of active metallic silver element, it can greatly affect the performance optimization of the catalyst. In addition, the present invention also adopts a strategy of doping with trace silver to regulate the composite material, and the in-situ grown trace silver significantly optimizes the performance of the overall composite material and improves its effect on the selectivity of carbon dioxide reduction.

[0074] In the present invention, the loading amount = m Ag / (m Ag +m 镧系氧化物 )×100%. Taking Example 1 as an example, the molar ratio of Ag:Pr = 1:2, and the loading amount = 107.8682 / (107.8682 + 2*1021.44 / 6) = 24.05%.

[0075] Example 1 Ag / Pr 6 O 11 Preparation of the catalyst

[0076] Figure 1 The process of catalyst preparation is shown.

[0077] Weigh 4.3501 g of Pr(NO 3 ) 3 ·6H 2 O, 0.8494 g of AgNO 3Pour them into a beaker, add an appropriate amount of deionized water, and stir on a magnetic stirring table until it becomes clear and transparent. Mix 5.84 g of ethylenediaminetetraacetic acid, 8.41 g of citric acid monohydrate, and 40 mL of ammonia water, stir until completely dissolved, and pour them into the beaker described above to prepare a complex solution. Continuously stir and heat the solution at 100 °C until it becomes gel-like. Send the gel-like mixture into an electric blast drying oven at 180 °C and dry it for 8 h to obtain a black, fluffy solid precursor. Take a part of the precursor and place it in a muffle furnace. In an air atmosphere, heat it to 800 °C at a heating rate of 4 °C / min and hold for 2 h. After natural cooling, take it out and grind it to obtain the final product, labeled as Ag / Pr 6 O 11 。

[0078] Example 2 Ag / La 2 O 3 Preparation of catalyst

[0079] Weigh 4.3301 g of La(NO 3 ) 3 ·6H 2 O, 0.8494 g of AgNO 3 Pour them into a beaker, add an appropriate amount of deionized water, and stir on a magnetic stirring table until it becomes clear and transparent. Mix 5.84 g of ethylenediaminetetraacetic acid, 8.41 g of citric acid monohydrate, and 40 mL of ammonia water, stir until completely dissolved, and pour them into the beaker described above to prepare a complex solution. Continuously stir and heat the solution at 100 °C until it becomes gel-like. Send the gel-like mixture into an electric blast drying oven at 180 °C and dry it for 8 h to obtain a black, fluffy solid precursor. Take a part of the precursor and place it in a muffle furnace. In an air atmosphere, heat it to 800 °C at a heating rate of 4 °C / min and hold for 2 h. After natural cooling, take it out and grind it to obtain the final product, labeled as Ag / La 2 O 3 。

[0080] Example 3 Ag / CeO 2 Preparation of catalyst

[0081] Weigh 4.3422 g of Ce(NO 3 ) 3 ·6H 2 O, 0.8494 g of AgNO 3Pour them into a beaker, add an appropriate amount of deionized water, and stir on a magnetic stirring table until clear and transparent. Mix 5.84 g of ethylenediaminetetraacetic acid, 8.41 g of citric acid monohydrate, and 40 mL of ammonia water and stir until completely dissolved, then pour them into the beaker described above to prepare a complex solution. Continuously stir and heat the solution at 100 °C until it becomes gel-like. Send the gel-like mixture into an electric blast drying oven at 180 °C and dry it for 8 h to obtain a black, fluffy solid precursor. Take a part of the precursor and place it in a muffle furnace. Under an air atmosphere, heat it to 800 °C at a heating rate of 4 °C / min and hold for 2 h. After natural cooling, take it out and grind it to obtain the final product, labeled as Ag / CeO 2 。

[0082] Example 4 Ag / Nd 2 O 3 Preparation of catalyst

[0083] Weigh 4.3885 g of Nd(NO 3 ) 3 ·6H 2 O, 0.8494 g of AgNO 3 Pour them into a beaker, add an appropriate amount of deionized water, and stir on a magnetic stirring table until clear and transparent. Mix 5.84 g of ethylenediaminetetraacetic acid, 8.41 g of citric acid monohydrate, and 40 mL of ammonia water and stir until completely dissolved, then pour them into the beaker described above to prepare a complex solution. Continuously stir and heat the solution at 100 °C until it becomes gel-like. Send the gel-like mixture into an electric blast drying oven at 180 °C and dry it for 8 h to obtain a black, fluffy solid precursor. Take a part of the precursor and place it in a muffle furnace. Under an air atmosphere, heat it to 800 °C at a heating rate of 4 °C / min and hold for 2 h. After natural cooling, take it out and grind it to obtain the final product, labeled as Ag / Nd 2 O 3 。

[0084] Comparative Example 1 Pr 6 O 11 Preparation of catalyst

[0085] Weigh 4.3501 g of Pr(NO 3 ) 3 ·6H 2Pour it into a beaker, add an appropriate amount of deionized water, and stir on a magnetic stirrer until it becomes clear and transparent. Mix 5.84 g of ethylenediaminetetraacetic acid, 8.41 g of citric acid monohydrate, and 40 mL of ammonia water, stir until completely dissolved, and pour it into the beaker described above to prepare a complex solution. Continuously stir and heat the solution at 100 °C until it becomes gel-like. Transfer the gel-like mixture to an electric blast drying oven at 180 °C and dry it for 8 h to obtain a black, fluffy solid precursor. Take a part of the precursor and place it in a muffle furnace. Under an air atmosphere, heat it to 800 °C at a heating rate of 4 °C / min and hold for 2 h. After natural cooling, take it out and grind it to obtain the final product, labeled as Pr 6 O 11 。

[0086] Preparation of the catalyst of Comparative Example 2 Ag powder

[0087] Weigh 0.8494 g of AgNO 3 Pour it into a beaker, add an appropriate amount of deionized water, and stir on a magnetic stirrer until it becomes clear and transparent. Mix 5.84 g of ethylenediaminetetraacetic acid, 8.41 g of citric acid monohydrate, and 40 mL of ammonia water, stir until completely dissolved, and pour it into the beaker described above to prepare a complex solution. Continuously stir and heat the solution at 100 °C until it becomes gel-like. Transfer the gel-like mixture to an electric blast drying oven at 180 °C and dry it for 8 h to obtain a black, fluffy solid precursor. Take a part of the precursor and place it in a muffle furnace. Under an air atmosphere, heat it to 800 °C at a heating rate of 4 °C / min and hold for 2 h. After natural cooling, take it out and grind it to obtain the final product, labeled as Ag powder (Ag powder).

[0088] Comparative Example 3 Ag+Pr 6 O 11 Preparation of the catalyst

[0089] Weigh a certain amount of Pr 6 O 11 from Comparative Example 1 and Ag from Comparative Example 2 according to a mass ratio of 7:3, physically grind and mix them, then place them in a muffle furnace. Under an air atmosphere, heat it to 800 °C at a heating rate of 4 °C / min and hold for 2 h to obtain the target product. The schematic diagrams of the sample structures of the two chemical synthesis and physical synthesis methods in Example 1 and Comparative Example 3 are as Figure 2 shown

[0090] XRD characterization of the material

[0091] The Ag / Pr 6 O 11 in Example 1 of the present invention and Pr 6 O 11 in Comparative Examples 1, 2, and 3, Ag powder, Ag+Pr 6 O11 The XRD (X-ray diffraction) results of Figure 3 are shown as follows. It can be seen that the synthesized Ag / Pr 6 O 11 and Ag+Pr 6 O 11 are both two-phase composite materials of Ag and Pr 6 O 11 . Among them, in the diffraction angle range of 20 - 30 degrees, the peak position of Ag+Pr 6 O 11 has a slight shift relative to that of Pr 6 O 11 , and the peak position of Ag / Pr 6 O 11 has a large shift relative to that of Pr 6 O 11 . This proves that the unit cell of the carrier in the chemically synthesized composite phase material expands, and part of the silver element is incorporated into the unit cell of the oxide during the synthesis process, resulting in a stronger interaction between the two phases of the composite phase material. The XRD results of Examples 2, 3, and 4 are shown as Figure 4 follows. The results all show that the composite material of silver / lanthanide oxide has been successfully synthesized, further proving the universality of the preparation method described in the present invention.

[0092] Evaluation of carbon dioxide electroreduction performance

[0093] Preparation of electrode paste. More than 10 mg of the catalyst prepared in the above examples or comparative examples, 10 mg of conductive carbon black (a conductive agent with almost no catalytic performance), 1 mL of ethanol (a dispersant), and 100 μL of Nafion solution (wt 5%) are ultrasonically mixed evenly to form a uniform black ink-like paste. The paste is drop-coated on the surface of a glassy carbon electrode and naturally dried to be used as a cathode working electrode.

[0094] Using the prepared catalyst electrode as the cathode working electrode, a silver-silver chloride reference electrode and a platinum sheet counter electrode are used to form a three-electrode system to test the electroreduction performance of carbon dioxide in an H-type electrolytic cell. The anode and cathode electrolytic cells are separated by a nafion proton membrane, and 0.1 M KHCO 3 electrolyte is filled on both the left and right. During the test, CO 2 is introduced into the electrolyte until it is saturated, and then a potentiostatic electrolysis test is carried out. The optimal potential is -1.2 V (VS RHE), and the optimal mass activity current density is 48.4 Ag -1 . The gas products obtained are analyzed by gas chromatography. At the same time, after the reaction, the catalyst is recovered from the cathode working electrode, which is the sample after the reaction (-AF).

[0095] 1. XPS, EPR, SEM, and TEM characterization of materials

[0096] The sample after the following reaction is the cathode working electrode after testing the performance of carbon dioxide electroreduction.

[0097] Figure 5 Shows Ag / Pr 6 O 11 and Ag / Pr 6 O 11 The XPS (X-ray photoelectron spectroscopy) of the sample after the reaction (Ag / Pr 6 O 11 -AF) reveals that part of the Ag element has indeed been successfully doped into praseodymium oxide and is rapidly fully reduced to Ag metal during the reaction. Figure 6 Shows Pr 6 O 11 、Ag+Pr 6 O 11 、Ag / Pr 6 O 11 and Ag / Pr 6 O 11 The XPS results of the O element of the sample after the reaction (Ag / Pr 6 O 11 -AF) show that the oxygen defect concentration of Ag / Pr 6 O 11 is the highest compared to the comparative example, and this ratio will further increase after the reaction. Figure 7 Shows the EPR (electron paramagnetic resonance) results of 4 samples, which also prove that Ag / Pr 6 O 11 and Ag / Pr 6 O 11 The samples after the reaction (Ag / Pr 6 O 11 -AF) have the highest oxygen defect concentration.

[0098] Figure 8 Shows the SEM (scanning electron microscopy) results of Ag / Pr 6 O 11 and the sample after the electrochemical reaction. It can be seen that the morphology of the sample changes little before and after the reaction, both are uniform spherical nanoparticles, but due to the electrochemical treatment and the in-situ precipitation process mentioned above Figure 5 , the average particle size of the catalyst after the reaction is further reduced, which is beneficial to the catalytic process. Figure 9 Further observation of the TEM (transmission electron microscopy) results of 6 O 11The diameter of the nanospheres is about 100 nm. Further high-resolution transmission electron microscopy tests also show that the lattice fringes of the two-phase materials contained in the nanospheres match well with those of praseodymium oxide and silver, and the diameters of the two phases exhibit a relatively rich two-phase interface, demonstrating the existence of an interaction between the metal and the support in the composite material.

[0099] 2. Carbon dioxide electroreduction performance

[0100] Figure 10 Shows the catalytic performance of the catalysts of Ag / Pr 6 O 11 of the present invention and Comparative Examples 1, 2, and 3. As Figure 10 shown in a, at a voltage of -1.2 V, the normalized mass activity of Ag / Pr 6 O 11 is 48.4 Ag -1 , which is much greater than that of Ag and Ag+Pr 6 O 11 of the comparative examples. This indicates that the reaction activity of the composite phase prepared by the chemical method is significantly improved. Figure 10 In b, Pr 6 O 11 shows almost no catalytic performance. The CO selectivity of Ag / Pr 6 O 11 is significantly higher than that of Ag and Ag+Pr 6 O 11 . At a voltage of -1.0 V, its Faraday efficiency is as high as 97%, and at a voltage of -1.2 V, its Faraday efficiency is as high as 98%. High CO selectivity is achieved within a relatively wide operating range, and the hydrogen evolution side reaction is significantly suppressed. Additionally, as can be seen in Figure 11 , during the carbon dioxide reduction reaction process of the Ag / Pr 6 O 11 catalyst, the Faraday efficiency for CO can basically maintain above 90% within 30 hours, indicating its good operating stability. Figure 12 The ECSA (electrochemical active surface area) of 6 O 11 shows that Ag / Pr 6 O 11 has a higher effective electrochemically reactive surface area compared to Ag and Ag+Pr Figure 13 The EIS (electrochemical impedance) results of 6 O 11 also show that Ag / Pr 6 O 11 has a lower electrochemical impedance compared to Ag and Ag+Pr

[0101] Figure 14 shows the Ag / La of Examples 2, 3, and 4 2 O 3 , Ag / CeO 2 and Ag / Nd 2 O 3 electrochemical results of carbon dioxide reduction. All the extended application cases can achieve a Faraday efficiency of more than 90% for CO, demonstrating the general superiority of the preparation method of the present invention and its applicability to other oxide systems. These prove that the present invention has certain industrial application value.

[0102] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

1. A supported Ag / lanthanide oxide nanocomposite material, characterized in that: Lanthanide oxides are used as carriers to load Ag.

2. The composite material according to claim 1, characterized in that The lanthanide oxide is Pr6O 11 , Any one or a combination of La2O3, CeO2 and Nd2O3.

3. The composite material according to claim 1 or 2, characterized in that: The Ag loading in the composite material is 20-25 wt %.

4. The composite material according to claim 1 or 2, characterized in that: The particle size of the composite material is 50- 200nm.

5. The method for preparing the composite material according to any one of claims 1 to 4, characterized in that: include: (1) dissolving lanthanide nitrate and silver nitrate in water to obtain a solution; (2) adding a metal ion complexing agent to the resulting solution, adjusting the pH to 6.5-7.5, and heating and stirring the gel-like mixture; (3) The obtained gel-like mixture is heated and dried to obtain a precursor powder; and the obtained precursor powder is calcined to obtain the composite material.

6. The preparation method according to claim 5, characterized in that: In step (1), the molar ratio of the lanthanide nitrate to silver nitrate is 1:1-4; preferably, the lanthanide nitrate is any one or a combination of praseodymium nitrate, lanthanum nitrate, cerium nitrate and neodymium nitrate; Preferably, in step (2), the metal ion complexing agent is ethylenediaminetetraacetic acid and citric acid monohydrate; The mass ratio of the silver nitrate, ethylenediaminetetraacetic acid and citric acid monohydrate is 1:5.8-7.8:8.9-10.9; Preferably, in step (2), the temperature of the heated and stirred gel-like mixture is 90-110°C; Preferably, in step (3), the heating and drying temperature is 170-190° C., and the heating and drying time is 7-10 h; Preferably, in step (3), the calcination temperature is 500-900° C., and the calcination time is 1-3 h.

7. An electrode, characterized in that: Made from the composite material according to any one of claims 1 to 4.

8. The electrode according to claim 7, characterized in that The composite material is used as a catalyst, and a conductive agent, a dispersant, and a binder are fully mixed to obtain a slurry; the obtained slurry is dripped on the surface of a carrier and naturally air-dried; preferably, the electrode uses a glassy carbon electrode or carbon fiber paper as a carrier; preferably, the conductive agent of the electrode is conductive carbon black; preferably, the dispersant of the electrode is an organic solvent, preferably ethanol or isopropanol; preferably, the binder of the electrode is Nafion solution or PTFE binder; preferably, the mass ratio of the composite material and the conductive agent is 1:0.5-2, preferably 1:0.7-1.2; preferably, the amount ratio of the composite material, the dispersant, and the binder is 10mg:0.7-1.2mL:90-120μL.

9. Use of the electrode according to claim 7 or 8 as a cathode working electrode in an electrochemical carbon dioxide reduction reaction.

10. The use according to claim 9, characterized in that The electrochemical carbon dioxide reduction reaction adopts a three-electrode system, the composite material is a cathode working electrode, silver-silver chloride is a reference electrode, and a platinum sheet or a graphite rod is a counter electrode; preferably, the electrochemical carbon dioxide reduction reaction is carried out in an H-type electrolytic cell, the H-type electrolytic cell adopts a 0.01-0.2M KHCO3 solution, and carbon dioxide gas is introduced to saturate the reaction.

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