Preparation method and application of rare earth ytterbium-doped copper oxide nano material

Abstract

The invention belongs to the technical field of nano material preparation, and provides a preparation method and application of a rare earth ytterbium-doped copper oxide nano material. The method comprises the following steps: dissolving rare earth ytterbium salt, copper salt and a surfactant in a solvent, and uniformly stirring; dissolving an organic ligand in a solvent; stirring and mixing the two solutions, transferring into a reaction kettle, and carrying out hydrothermal reaction; and centrifugally washing the obtained product with ethanol, and drying to obtain the rare earth ytterbium doped metal organic precursor nano material. And placing the obtained nano material in a muffle furnace for high-temperature calcination to obtain the rare earth ytterbium doped copper oxide material. The preparation method provided by the invention is simple, green, pollution-free and high in practical degree, and the obtained rare earth ytterbium-doped copper oxide nano material can be used as a catalyst for synthesizing ammonia by electrolytic nitrate reduction, and shows that the rare earth ytterbium-doped copper oxide nano material has relatively high ammonia yield and Faraday efficiency for synthesizing ammonia by nitrate reduction.

Description

Technical Field

[0001] The invention belongs to the technical field of nano material preparation, and relates to a preparation method and application of a rare earth ytterbium-doped copper oxide nano material. Background Art

[0002] The ammonia chemical industry forms the foundation of modern agriculture and human society. Ammonia production worldwide is achieved through the traditional Haber-Bosch process, which requires high temperature and high pressure reaction conditions, consumes large amounts of energy, and releases large amounts of carbon dioxide. Therefore, utilizing electricity generated by renewable energy sources such as solar, wind, and tidal energy to synthesize ammonia through electrochemical catalysis by reducing nitrates is considered a new technology for future green ammonia synthesis.

[0003] Electrocatalytic nitrate reduction (NO3RR) is an ideal green strategy for ammonia synthesis and can also simultaneously treat nitrate pollution from industrial and domestic wastewater. Nitrate electrochemical reduction to ammonia is a complex process involving eight electron transfers, involving a series of reaction intermediates and pathways. The nitrate electroreduction process is divided into two parts: an indirect autocatalytic reduction pathway and a direct electrocatalytic reduction pathway. The indirect reduction pathway, mediated by active hydrogen, is more favorable for improving the selectivity of ammonia synthesis (Wang, Y.; Wang, C.; Li, M.; Yu, Y.; Zhang, B., Nitrate Electroreduction: Mechanism Insight, In Situ Characterization, Performance Evaluation, and Challenges. Chem. Soc. Rev. 2021, 50, 6720-6733.). Furthermore, because the reaction occurs in solution, the hydrogen evolution reaction (HER) is a major side reaction that reduces the Faradaic efficiency of NH3 production. Therefore, one of the key challenges for the large-scale implementation of electrochemical NO3RR technology is the identification of efficient electrocatalytic materials that exhibit high activity and selectivity for the desired product (ammonia).

[0004] Since the d orbital energy level of copper (Cu) is similar to that of NO3 - The lowest unoccupied molecular orbital (LUMO) of Cu is similar to that of Cu, indicating that Cu has the function of promoting electron transfer. This makes Cu not only have a strong adsorption capacity for nitrate, but also have a strong adsorption capacity for NO3 - Reduction to NO2 -The rapid reduction kinetics in the rate-determining step of the reaction also make copper-based materials more catalytic for the reduction of nitrate to ammonia. Furthermore, due to the relatively weak HER performance of Cu itself, copper-based materials have a good inhibitory effect on the competitive HER. However, due to their strong adsorption of intermediates in the NO3RR, copper-based materials are easily poisoned. In addition, the insufficient coverage of active hydrogen (*H) on Cu at low negative potentials further hinders the subsequent hydrogenation step (Zhang M., Zhang Z., Zhang S., Zhuang Z., Song K., Paramaiah K., Yi M., Huang H., and Wang D., Efficient Electrochemical Nitrate Reduction to Ammonia Driven by a FewNanometer-Confined Built-In Electric Field, ACS Catal. 2024, 14, 10437-10446; Ouyang X., Qiao W., Yang Y., Xi B., Yu Y., Wu Y., Fang J., Li P., Xiong S., Intensifying Interfacial Reverse Hydrogen Spillover for BoostedElectrocatalytic Nitrate Reduction to Ammonia, Angew. Chem. Int. Ed. 2025, 64, e202422585). Therefore, by introducing other functional components into copper-based materials and finely regulating the structure and function of the materials, it is expected to solve the problems of intermediate conversion and active hydrogen supply during the electrochemical reduction of nitrate, thereby improving the catalytic performance.

[0005] Currently, commonly used functional components include precious metals (such as Pt and Rh) and cheap transition metals (such as Co and Ti), so new functional components should also be further explored.

[0006] Although the Cu-TiO2 system has excellent stability, its inherent defects limit its application prospects. This wide-bandgap semiconductor material requires the presence of precious metal co-catalysts to exhibit ideal activity, which greatly increases the preparation cost. More importantly, the lack of effective active sites on its surface causes the reaction to often remain in the nitrite intermediate state, making it difficult to achieve complete nitrate reduction (Niu S., Chu L., Wu C., Ni Y., Du L., Wu C., Cai Y., Si N., Gu X., Jiang D., Feng Y., Zhao Q., Li J, Comprehensive Experimental Design of CopperDoped Titanium Dioxide Electrocatalytic Reduction of Nitrate to Ammonia Chin. J. Chem. Educ. 2024, 45 (22), 34–42.).

[0007] In contrast, rare earth element doping, especially cerium (Ce) doping into the catalyst structure, has been widely proven to significantly improve the catalytic activity of the catalyst. 3+ and Ce 4+ Due to the redox process between Ce and Ce, Ce-related compounds have mixed electronic / ionic conductivity, which can tune catalytic performance, such as hydrogen production or CO oxidation. At the same time, the redox process of Ce can generate oxygen vacancies (Ov), thereby improving the catalytic activity.

[0008] These studies demonstrate that, thanks to their unique electronic structure, the introduction of rare earth elements into copper-based catalysts can help modulate the electronic structure and increase the number of active sites. Furthermore, rare earth elements generally have a stronger affinity for hydrogen than copper, and their introduction can aid in the hydrogenation of nitrogen species during the NO₃RR process. Experiments have confirmed that this novel material system achieves significant improvements in activity, selectivity, and Faradaic efficiency, providing a superior solution for nitrate treatment. Summary of the Invention

[0009] The purpose of the present invention is to provide a preparation method and application of a rare earth ytterbium (Yb)-doped copper oxide nanomaterial. When the material of the present invention is used as a catalyst, it exhibits a high ammonia production rate and Faradaic efficiency for the synthesis of ammonia by nitrate reduction.

[0010] The technical solution of the present invention:

[0011] A method for preparing rare earth ytterbium-doped copper oxide nanomaterial, comprising the following steps:

[0012] Step 1: Dissolve rare earth ytterbium salt, copper salt, and surfactant in a solvent and stir evenly; dissolve organic ligand in a solvent; stir and mix the two solutions, transfer them to a reactor, and perform a hydrothermal reaction; wash the obtained product with ethanol by centrifugation and then dry it to obtain a Yb-Cu-based metal organic precursor nanomaterial;

[0013] Step 2: placing the Yb-Cu based metal organic precursor nanomaterial obtained in step 1 in a muffle furnace and calcining it at high temperature to obtain rare earth ytterbium doped copper oxide nanomaterial.

[0014] In step 1, the molar ratio of the rare earth ytterbium salt to the copper salt is 1:(10-40), the molar ratio of the copper salt to the organic ligand is (1-5):1, and the mass ratio of the surfactant to the total mass of the rare earth ytterbium salt and the copper salt is (4-8):10.

[0015] The rare earth ytterbium salt is ytterbium nitrate, ytterbium chloride or ytterbium acetate.

[0016] The copper salt is copper nitrate, copper chloride or copper acetate.

[0017] The surfactant is polyvinyl pyrrolidone (PVP) or polyethylene glycol (PEG).

[0018] The solvent is DMF alone or a mixed solvent of DMF and ethanol.

[0019] The organic ligand is diphenyl dicarboxylic acid, terephthalic acid or trimesic acid.

[0020] The temperature of the hydrothermal reaction is 80-180° C., and the time is 1-5 hours.

[0021] The drying temperature is 50-100° C. and the drying time is 8-24 hours.

[0022] In step 2, the high-temperature calcination temperature is 350-600°C, the time is 1-4 hours, and the heating rate is 2-5°C / min.

[0023] The present invention also provides a rare earth ytterbium-doped copper oxide nanomaterial obtained by the above preparation method, which has a hollow regular octahedral structure with an uneven surface.

[0024] The present invention also provides the use of the rare earth ytterbium-doped copper oxide nanomaterial as a catalyst in electrochemical nitrate reduction to synthesize ammonia.

[0025] The present invention has the following beneficial effects: The Yb-CuO nanomaterial prepared in this invention has a unique hollow octahedral structure and exhibits excellent electrocatalytic activity for nitrate reduction when used as a catalyst. Furthermore, the preparation method is relatively simple, the raw materials are readily available, and the material has high practical value, which is of great significance for the design, preparation, and application of catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope image of the Yb-Cu based metal organic precursor nanomaterial prepared in Example 3.

[0027] Figure 2 This is a scanning electron microscope image of the Yb-CuO nanomaterial prepared in Example 5.

[0028] Figure 3 This is the XRD pattern of the Yb-CuO nanomaterial tested in Example 7.

[0029] Figure 4 Polarization curves of the Yb-CuO nanomaterial tested in Example 8 relative to the Ag / AgCl electrode in different electrolytes.

[0030] Figure 5 This is a graph showing ammonia production and Faraday efficiency of the Yb-CuO nanomaterial tested in Example 8.

[0031] Figure 6 This is a comparison chart of ammonia production and Faradaic efficiency of the nanomaterials tested in Comparative Example 2, Comparative Example 4 and Example 8 at a potential of -0.5 V (relative to the reversible hydrogen electrode). DETAILED DESCRIPTION

[0032] The specific implementation scheme of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0033] Example 1

[0034] Preparation of Yb-Cu based metal organic precursor nanomaterials

[0035] Dissolve Cu(AcO)2 (302.1 mg), YbCl3 (11.6 mg), and PEG (235 mg) in DMF (10 mL). Dissolve biphenyldicarboxylic acid (89.9 mg) in DMF (10 mL). Combine the two solutions and stir thoroughly for 10 minutes. Transfer the mixture to a reactor and hydrothermally react at 170°C for 1 hour. The resulting product is centrifuged and washed with ethanol three times before drying in a 50°C oven to yield a Yb-Cu-based metal-organic precursor nanomaterial.

[0036] Example 2

[0037] Preparation of Yb-Cu based metal organic precursor nanomaterials

[0038] Cu(NO₃)₂∙3H₂O (361.6 mg), Yb(AcO)₃ (57.64 mg), and PVP (335 mg) were dissolved in a mixture of DMF (7 mL) and ethanol (3 mL). Terephthalic acid (166.1 mg) was dissolved in a mixture of DMF (7 mL) and ethanol (3 mL). The two solutions were then mixed and stirred for 10 minutes. The mixture was then transferred to a reactor and hydrothermally reacted at 160°C for 1.5 hours. The resulting product was centrifuged and washed with ethanol three times before being dried in a 70°C oven to obtain a Yb-Cu-based metal-organic precursor nanomaterial.

[0039] Example 3

[0040] Preparation of Yb-Cu based metal organic precursor nanomaterials

[0041] Cu(NO₃)₂∙3H₂O (401.8 mg), Yb(NO₃)₃ (31.6 mg), and PVP (266.6 mg) were dissolved in DMF (10 mL). Trimesic acid (176.7 mg) was dissolved in DMF (10 mL). The two solutions were then mixed and stirred for 10 minutes. The mixture was then transferred to a reactor and hydrothermally reacted at 100°C for 2 hours. The resulting product was centrifuged and washed with ethanol three times before being dried in a 60°C oven to obtain a Yb-Cu-based metal-organic precursor nanomaterial.

[0042] Example 4

[0043] Preparation of Yb-Cu based metal organic precursor nanomaterials

[0044] CuCl₂ (233.5 mg), Yb(NO₃)₃ (22.1 mg), and PEG (179 mg) were dissolved in DMF (10 mL). Trimellitic acid (119.9 mg) was dissolved in DMF (10 mL). The two solutions were then mixed and stirred for 10 minutes. The mixture was then transferred to a reactor and hydrothermally reacted at 150°C for 2 hours. The resulting product was centrifuged and washed with ethanol three times before being dried in a 60°C oven to obtain a Yb-Cu-based metal-organic precursor nanomaterial.

[0045] Example 5

[0046] Preparation of Yb-CuO nanomaterials

[0047] The Yb-Cu-based metal organic precursor nanomaterial (10 mg) from Example 3 was placed in a porcelain boat in a muffle furnace and calcined under an oxygen atmosphere at 400°C, a heating rate of 2°C / min, and a calcination time of 2 hours.

[0048] After high temperature treatment of Yb-Cu based metal organic precursor nanomaterials, Yb-CuO nanoparticles with obvious granularity, hollow and uneven surface are obtained, such as Figure 2 As shown, the particle size obtained after calcination is almost unchanged.

[0049] Example 6

[0050] Preparation of Yb-CuO nanomaterials

[0051] The Yb-Cu-based metal organic precursor nanomaterial (10 mg) from Example 3 was placed in a porcelain boat in a muffle furnace and calcined under an oxygen atmosphere at 450°C, a heating rate of 5°C / min, and a calcination time of 1.5 hours.

[0052] Comparative Example 1

[0053] Preparation of CuO nanomaterials

[0054] Cu(NO₃)₂∙3H₂O (401.8 mg) and PVP (266.6 mg) were dissolved in DMF (10 mL). Trimellitic acid (176.7 mg) was dissolved in DMF (10 mL). The two solutions were then mixed and stirred for 10 minutes. The mixture was then transferred to a reactor and hydrothermally reacted at 100°C for 2 hours. The resulting product was centrifuged and washed with ethanol three times before being dried in a 60°C oven to obtain a Cu-based metal organic precursor nanomaterial. The Cu-based metal organic precursor nanomaterial (10 mg) was placed in a porcelain boat in a muffle furnace and calcined under an oxygen atmosphere at 400°C, a heating rate of 2°C / min, and a calcination time of 2 hours to obtain a CuO nanomaterial.

[0055] Comparative Example 2

[0056] Test of catalytic performance of CuO nanomaterials

[0057] At a potential of -0.5 V (relative to the reversible hydrogen electrode), an IT test was performed, and the color was developed by indophenol blue spectrophotometry. Quantitative analysis was performed to obtain the ammonia yield and Faradaic efficiency at this potential. The yield and Faradaic efficiency of CuO nanomaterials for synthesizing ammonia were 27280.3 μg h, respectively. −1 mg cat. −1 and 78.8%.

[0058] Comparative Example 3

[0059] Preparation of Gd-CuO nanomaterials

[0060] Cu(NO₃)₂∙3H₂O (401.8 mg), Gd(NO₃)₂∙6H₂O (39.7 mg), and PVP (266.6 mg) were dissolved in DMF (10 mL). Trimellitic acid (176.7 mg) was dissolved in DMF (10 mL). The two solutions were then mixed and stirred for 10 minutes. The mixture was then transferred to a reactor and hydrothermally reacted at 100°C for 2 hours. The resulting product was centrifuged and washed with ethanol three times before being dried in a 60°C oven to obtain a Gd-Cu-based metal-organic precursor nanomaterial. The Gd-Cu-based metal-organic precursor nanomaterial (10 mg) was placed in a porcelain boat in a muffle furnace and calcined under an oxygen atmosphere at 400°C, a heating rate of 2°C / min, and a calcination time of 2 hours to obtain the Gd-CuO nanomaterial.

[0061] Comparative Example 4

[0062] Catalytic performance test of Gd-CuO nanomaterials

[0063] At a potential of -0.5 V (vs. reversible hydrogen electrode), an IT test was performed, and the color was developed by indophenol blue spectrophotometry. Quantitative analysis was performed to obtain the ammonia yield and Faradaic efficiency at this potential. The yield and Faradaic efficiency of Gd-CuO nanomaterials for synthesizing ammonia were 14206.4 μg h, respectively. −1 mg cat. −1 and 71.8%.

[0064] Example 7

[0065] Chemical structure test of Yb-CuO nanomaterials

[0066] XRD characterization showed that the introduction of Yb did not change the overall crystal structure of CuO ( Figure 3 ), so this synthesis method is of great significance to improving the overall stability and electrocatalytic performance of the material.

[0067] Example 8

[0068] Catalytic performance test of Yb-CuO nanomaterials

[0069] The IT test was carried out at potentials of -0.3V, -0.4V, -0.5V, -0.6V and -0.7V (relative to the reversible hydrogen electrode), and the color was developed by indophenol blue spectrophotometry and quantitative analysis was performed. Figure 4 As shown in Figure 2, the catalytic performance of the tested Yb-CuO nanomaterials relative to the hydrogen evolution performance of the Ag / AgCl electrode. Figure 5 As shown in Figure 2, the yield and Faradaic efficiency of Yb-CuO nanomaterials for synthesizing ammonia are 32737.5 μg h−1 mg cat. −1 and 88.7%. Figure 6 Comparison charts show that the catalytic performance of the Yb-CuO nanomaterial is significantly higher than that of undoped CuO nanomaterials and Gd-CuO nanomaterials with the same doping ratio. Its unique hollow octahedral structure enables it to exhibit excellent electrocatalytic nitrate reduction activity as a catalyst, demonstrating that the introduction of Yb plays a significant role in improving the performance of electrocatalytic nitrate reduction to ammonia synthesis.

Claims

1. A method for preparing rare earth ytterbium-doped copper oxide nanomaterial, characterized in that: Here are the steps: Step 1: Dissolve rare earth ytterbium salt, copper salt, and surfactant in a solvent and stir evenly; dissolve organic ligand in a solvent; stir and mix the two solutions, transfer them to a reactor, and perform a hydrothermal reaction; wash the obtained product with ethanol by centrifugation and then dry it to obtain a Yb-Cu-based metal organic precursor nanomaterial; Step 2: placing the Yb-Cu based metal organic precursor nanomaterial obtained in step 1 in a muffle furnace and calcining it at high temperature to obtain rare earth ytterbium doped copper oxide nanomaterial.

2. The preparation method according to claim 1, characterized in that In step one, The rare earth ytterbium salt is ytterbium nitrate, ytterbium chloride or ytterbium acetate; The copper salt is copper nitrate, copper chloride or copper acetate; The surfactant is polyvinyl pyrrolidone or polyethylene glycol; The solvent is DMF alone or a mixed solvent of DMF and ethanol; The organic ligand is diphenyl dicarboxylic acid, terephthalic acid or trimesic acid.

3. The preparation method according to claim 1, characterized in that In step one, The molar ratio of the rare earth ytterbium salt to the copper salt is 1:(10-40), the molar ratio of the copper salt to the organic ligand is (1-5):1, and the mass ratio of the surfactant to the total mass of the rare earth ytterbium salt and the copper salt is (4-8):

10.

4. The preparation method according to claim 1, characterized in that In step one, The temperature of the hydrothermal reaction is 80-180° C., and the time is 1-5 hours.

5. The preparation method according to claim 1, characterized in that In step one, The drying temperature is 50-100° C. and the drying time is 8-24 hours.

6. The preparation method according to claim 1, characterized in that In step 2, The high-temperature calcination temperature is 350-600°C, the time is 1-4 hours, and the heating rate is 2-5°C / min.

7. The preparation method according to claim 1, characterized in that The rare earth ytterbium-doped copper oxide nanomaterial has a hollow regular octahedral structure with an uneven surface.

8. Use of a rare earth ytterbium-doped copper oxide nanomaterial obtained by the preparation method according to any one of claims 1 to 7 in electrochemical nitrate reduction to synthesize ammonia.

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