Three-dimensional cu nanowire material with multi-level defects and preparation method and application thereof
By constructing a three-dimensional Cu nanowire material with multi-level defects, the problems of reaction path deviation and active hydrogen supply in NOxRR electroreduction ammonia synthesis were solved, realizing efficient and stable electrocatalytic ammonia synthesis and promoting the development of low-carbon ammonia synthesis technology.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- YUNNAN UNIV
- Filing Date
- 2026-03-21
- Publication Date
- 2026-06-16
AI Technical Summary
In existing NOxRR electroreduction ammonia synthesis technology, the reaction path is deviated, the selectivity and Faraday efficiency are low, and the active hydrogen supply and hydrogen evolution reaction are difficult to reconcile, resulting in rapid catalyst deactivation and by-product generation, making it difficult to achieve efficient ammonia synthesis under mild conditions.
We constructed a three-dimensional Cu nanowire material with multi-level defects, integrating atomic-level point defects, crystal interface defects, and mesoscopic porous defects. Through electrochemical methods, we formed a multi-level defect synergistic system on the copper nanowire framework, optimized reactant mass transfer and key intermediate transformation, and precisely controlled H generation and utilization.
This technology enables efficient and stable electrocatalytic reduction of nitrate/nitrite to ammonia under mild conditions, with a Faraday efficiency approaching 100%. It provides a green and low-carbon ammonia synthesis technology with significant application potential.
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Figure CN122214907A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrocatalytic ammonia synthesis technology, specifically to a multi-level defect three-dimensional copper nanowire material for the electrocatalytic reduction of nitrite to ammonia synthesis, its preparation method, and its application. Background Technology
[0002] Ammonia (NH3) is a core raw material for the fertilizer industry and a key precursor for important chemicals such as synthetic fibers and pharmaceuticals. Its high hydrogen content and ease of liquefaction and storage make it a highly promising green hydrogen energy carrier. Currently, global ammonia synthesis almost entirely relies on the Haber-Bosch process. While this process is mature, it requires extreme conditions of high temperature (400-500℃) and high pressure (15-25MPa), consuming approximately 1-2% of global energy supply annually and generating massive amounts of carbon dioxide emissions. This contradicts the global strategy of "carbon neutrality." Therefore, developing sustainable ammonia synthesis technologies that operate under milder conditions (such as ambient temperature and pressure) and are coupled with renewable energy sources has become a focus of attention for both academia and industry.
[0003] Among the many emerging routes, electrocatalytic nitrogen reduction (NRR) and nitrate / nitrite reduction (NO) are... x The synthesis of ammonia (RR) has attracted much attention. Among these, NO, a widely present water pollutant, is a key component. x The RR electrocatalytic reduction pathway using nitrogen source is more easily activated due to the good water solubility of nitrogen source and the fact that the N=O bond energy (204 kJ / mol) is much lower than the N≡N bond energy (941 kJ / mol). It exhibits higher thermodynamic feasibility and reaction kinetic potential and is considered one of the most promising technical pathways for achieving efficient ammonia synthesis at low temperature and low pressure.
[0004] However, NO x RR electroreduction synthesis of ammonia (NO x The practical application of NOx-to-NH3 (RR-to-NH3) still faces significant scientific and technological challenges. The core issue lies in the complex multi-proton, multi-electron reaction process (NOx-to-NH3). - →NH3, involving 6 / 8e - and 6 / 8H + The reaction is highly susceptible to path deviation, leading to low selectivity and Faraday efficiency. Specifically: First, excessive adsorption and accumulation of reaction intermediates (such as NO and NH2OH) on the catalyst surface not only poisons the active sites, causing rapid catalyst deactivation, but also induces competitive reactions that produce byproducts such as nitrogen (N2) or nitrous oxide (N2O), severely reducing ammonia selectivity. Second, there is an irreconcilable competition between the supply of active hydrogen (H) required for the reaction and the hydrogen evolution reaction (HER). In aqueous electrolytes, HER is generally thermodynamically more efficient than NO. xRelative oxidative stress (RR) is more likely to occur. If the catalyst's ability to dissociate water to produce H₂ is insufficient, then NO₂ will be more likely to occur. x RR will be limited by "hydrogen starvation"; if H generation is too rapid or too strong, HER will dominate, consuming a large number of electrons and protons, which will also lead to low ammonia yield and efficiency. Therefore, designing a catalyst that can simultaneously optimize reactant mass transfer, promote the transformation of key intermediates, and precisely control the dynamic balance between H generation and utilization is the key to breaking through the current bottleneck.
[0005] In recent years, defect engineering has been considered an effective strategy for regulating the electronic structure, surface adsorption behavior, and reaction kinetics of catalysts. For example, defects such as vacancies and grain boundaries can create coordination-unsaturated active sites, altering the adsorption strength of key species. However, single types of defects are often insufficient to synergistically address NO. x The RR process presents numerous challenges. Therefore, how to construct a catalytic system with multi-level and multi-dimensional defect synergistic effects through ingenious material design to achieve efficient and highly selective control of complex reaction networks is a core problem that urgently needs to be solved in this field, and it is also the starting point of this invention. Summary of the Invention
[0006] To address the shortcomings and deficiencies of existing technologies, this invention provides a method for preparing a three-dimensional Cu nanowire material with multi-level defects. This method uses copper nanowires as a framework and constructs a multi-level defect synergistic system on the surface, consisting of point defects formed by atomic absence, surface defects formed by crystal interfaces, and bulk defects formed by porous structures. This three-dimensional Cu nanowire material with multi-level defects can be applied in the electrocatalytic reduction of nitrate or nitrite to synthesize ammonia.
[0007] The objective of this invention is achieved through the following technical solution: 1. The copper material is sequentially immersed in acetone, ethanol, and hydrochloric acid solutions for ultrasonic pretreatment; 2. In an electrolytic cell filled with electrolyte, pretreated copper material is used as the anode and an inert electrode as the cathode, both immersed in the electrolyte, at a current of 40~80 mA / cm². 2 The reaction was carried out at a constant potential of 1~10 V for 5~30 min. After the reaction was completed, the electrode was washed with deionized water and dried under vacuum to obtain electrode A. The copper material is one of copper foam, copper mesh, and copper foil; the inert electrode is one of platinum wire electrode, platinum sheet electrode, and graphite electrode; the electrolyte is a 0.1~3 mol / L sodium hydroxide or potassium hydroxide solution. 3. Place electrode A in a solution containing organic ligands, allow it to stand at room temperature or sonicate it, wash it with deionized water, and dry it at room temperature to obtain electrode B; The organic ligand is terephthalic acid or trimesic acid, and the solution containing the organic ligand is a methanol aqueous solution or an ethanol aqueous solution with a volume concentration of 70-90% containing 1-10 mg / mL of organic ligand. 4. Using a three-electrode system, with electrode B as the working electrode, one end of the working electrode, the counter electrode, and the reference electrode are placed in an electrolytic cell containing electrolyte. A constant voltage of -0.2V to -2.0V is applied to the three-electrode system for 60 to 300 minutes to obtain a three-dimensional Cu nanowire material with multi-level defects.
[0008] The electrolyte is a 0.1~1 mol / L sodium sulfate solution, potassium sulfate solution, sodium hydroxide solution, or potassium hydroxide solution; the inert electrode is the counter electrode, and Ag / AgCl or saturated calomel is the reference electrode.
[0009] 4. The three-dimensional Cu nanowire material with multi-level defects was applied to the electrocatalytic reduction of nitrate / nitrite to ammonia. The experimental results showed that the material exhibited a Faraday efficiency of nearly 100% and high reactivity, and has important application prospects in the fields of nitrogen cycle and ammonia synthesis.
[0010] The beneficial effects of this invention are: (1) This invention constructs a multi-level defect synergistic system: atomic-level point defects, crystal interface defects and mesoporous defects are successfully integrated on a three-dimensional copper nanowire framework, realizing cross-dimensional defect engineering from the atomic scale to the nanoscale; this multi-level defect structure provides a unique combination of active sites and synergistic effect for efficient catalysis. (2) This material provides a novel, efficient and stable catalyst for green and low-carbon electrochemical ammonia synthesis technology. It has significant application potential not only in artificial nitrogen cycling and renewable energy storage, but its multi-level defect design concept can also be extended to other complex multi-proton-multi-electron electrocatalytic reactions. Attached Figure Description
[0011] Figure 1 SEM images of copper foam (Fig. a, b), Cu(OH)2 nanowires (Fig. c, d), Cu(OH)2-MOF nanowires (Fig. e, f), and three-dimensional Cu nanowire copper foam with multi-level defects (Fig. g, h); Figure 2 The images show point defects formed by the absence of Cu atoms. Figure a is a HAADF-STEM image, figure b is a magnified view of the region in figure a, figure c is an atomic intensity contour plot, and figure d is an atomic intensity contour plot of the region in figure c. Figure 3 The images show surface defects formed by crystal interfaces, where image a is a HAADF-STEM image and image b is a magnified view of the region. Figure 4A schematic diagram of volume defects formed by porous structures; Figure 5 Figure 1 shows the ammonia synthesis performance of three-dimensional Cu nanowires with multi-level defects as catalysts, where Figure 2a is the ammonia yield and Figure 3b is the ammonia Faraday efficiency. Figure 6 The graphs show the performance of ammonia synthesis using copper foam as a catalyst, where graph a is the ammonia yield and graph b is the ammonia Faraday efficiency.
[0012] Figure 7 Figure 1 shows the performance of ammonia synthesis using Cu nanowires as a catalyst, where Figure 2a shows the ammonia yield and Figure 3b shows the ammonia Faraday efficiency. Detailed Implementation
[0013] The method of the present invention will be described in detail below with reference to specific embodiments. These embodiments are implemented under the premise of the technical solution of the present invention, but the protection scope of the present invention is not limited to the following embodiments. Example 1
[0014] (1) The copper foam was sequentially immersed in acetone, anhydrous ethanol, and 3 mol / L hydrochloric acid solution for ultrasonic pretreatment for 20 min each; the treated copper foam was used as the anode, a platinum sheet as the counter electrode, and 1 mol / L sodium hydroxide solution as the electrolyte. The copper foam was immersed in the electrolyte with an immersion area of 1 cm². 2 SEM images of copper foam, such as Figure 1 As shown in figures a and b, the surface of the copper foam is smooth and flat, providing a foundation for the subsequent growth of Cu(OH)₂ nanowires. A constant current of 40 mA is applied to the electrode, the constant potential is 1.8 V, the reaction time is 6 min, and it is then allowed to air dry to obtain the Cu(OH)₂ nanowire electrode. Figure 1 As shown in c and d, it can be seen from the figure that a dense and uniform Cu(OH)2 nanowire array grows on the surface of the copper foam, with a smooth surface and regular morphology. (2) Weigh 0.1 g of terephthalic acid and dissolve it in 12.94 mL of 85% ethanol aqueous solution. Place the electrode with Cu(OH)2 nanowires in the terephthalic acid solution and let it stand at room temperature for 10 min. Remove it and rinse it with anhydrous ethanol and deionized water in sequence to obtain the Cu(OH)2-MOF nanowire electrode. Figure 1 As shown in e and f, it can be seen from the figures that a large number of sheet-like metal-organic framework structures are generated on the surface of the nanowires, uniformly wrapping the nanowires. (3) Using Cu(OH)2-MOF nanowire electrodes as the working electrode, platinum sheets as the counter electrode, Ag / AgCl as the reference electrode, and 0.1 mol / L sodium sulfate solution as the electrolyte, a three-electrode system was formed. A constant potential of -1 V (vs. RHE) was applied to it for 120 min to obtain three-dimensional Cu nanowire materials (d-Cu NWs) with multi-level defects. The SEM images are shown below. Figure 1 As shown in g and h, the surface of the Cu nanowire material is rich in defects and pores. The microstructure of the catalyst was characterized using a spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscopy, and the results are shown in [Figure number missing]. Figure 2-4 As can be seen from the figure, Cu vacancies exist, i.e. "point defects", abundant grain boundary defects are embedded in the crystal plane, i.e. "plane defects", and abundant nanopore defects, i.e. "volume defects", exist on the surface of copper nanowires.
[0015] (4) Electrocatalytic reduction of nitrite to synthesize ammonia A three-dimensional Cu nanowire material with multi-level defects was used as the working electrode, a platinum sheet as the counter electrode, Ag / AgCl as the reference electrode, and a 0.5 mol / L KOH solution containing 2000 ppm nitrite as the electrolyte to form a three-electrode system. A constant potential of 0 to -0.2 V (vs. RHE) was applied to the system for 120 min, and the ammonia concentration after the reaction was detected. The results are shown in [Figure number missing]. Figure 5 As shown in the figure, after 2 hours of electrolysis at -0.2V, the ammonia formation rate of the d-Cu NWs electrode reached as high as 15032.8 µg / h. -1 cm -2 The Faraday efficiency is 103%, and it remains close to 100% across the entire voltage range.
[0016] Comparative Example 1: Using the pretreated copper foam (Cu Foam) from step (1) as the working electrode, electrocatalytic reduction of nitrite to ammonia was performed using the same method as above. The results are shown in [Figure 1]. Figure 6 As can be seen from the figure, the ammonia yield and Faraday efficiency are unsatisfactory throughout the entire voltage range, and there is basically no activity for electrocatalytic reduction of nitrite to ammonia.
[0017] Comparative Example 2: Using the Cu(OH)2 nanowire electrode prepared in step (1) as the working electrode, the platinum sheet as the counter electrode, Ag / AgCl as the reference electrode, and 0.1 mol / L sodium sulfate solution as the electrolyte, a three-electrode system was formed. A constant potential of -1 V (vs. RHE) was applied to it for 120 min to obtain Cu nanowire electrodes (Cu NWs). Using a Cu nanowire electrode as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, the electrocatalytic reduction of nitrite to ammonia was performed using the same method as above. The results are shown in [Figure 1]. Figure 7 As shown in the figure, after electrolysis at -0.2V for 2 hours, the ammonia generation rate of the Cu nanowire electrode reached as high as 10391 µg h⁻¹. -1 cm -2 The Faraday efficiency is 92%, which is lower than that of three-dimensional Cu nanowires with multi-level defects.
Claims
1. A method for preparing a three-dimensional Cu nanowire material with multi-level defects, characterized in that, The steps are as follows: (1) In an electrolytic cell containing electrolyte, pretreated copper material is used as the anode and an inert electrode is used as the cathode, both immersed in the electrolyte, at a current of 40~80 mA / cm. 2 After reacting at a constant potential of 1-10 V for 5-30 min, the electrode was washed with deionized water and dried under vacuum to obtain electrode A. (2) Place electrode A in a solution containing organic ligands, let it stand at room temperature or sonicate it, wash it with deionized water, and dry it at room temperature to obtain electrode B; (3) Using a three-electrode system, with electrode B as the working electrode, one end of the working electrode, the counter electrode and the reference electrode are placed in an electrolytic cell containing electrolyte. A constant voltage of -0.2V to -2.0V is applied to the three-electrode system for 60 to 300 minutes to obtain a three-dimensional Cu nanowire material with multi-level defects.
2. The method for preparing three-dimensional Cu nanowire materials with multi-level defects according to claim 1, characterized in that: The copper material is one of foamed copper, copper mesh, or copper foil, and the inert electrode is one of platinum wire electrode, platinum sheet electrode, or graphite electrode.
3. The method for preparing three-dimensional Cu nanowire materials with multi-level defects according to claim 1, characterized in that: In step (2), the electrolyte is a 0.1-3 mol / L sodium hydroxide or potassium hydroxide solution.
4. The method for preparing three-dimensional Cu nanowire materials with multi-level defects according to claim 1, characterized in that: The organic ligand is terephthalic acid or pyromellitic acid, and the solution containing the organic ligand is a methanol aqueous solution or an ethanol aqueous solution with a volume concentration of 70-90% containing 1-10 mg / mL of organic ligand.
5. The method for preparing three-dimensional Cu nanowire materials with multi-level defects according to claim 1, characterized in that: The electrolyte in step (4) is a 0.1~1 mol / L sodium sulfate solution, potassium sulfate solution, sodium hydroxide solution or potassium hydroxide solution.
6. The three-dimensional Cu nanowire material with multi-level defects prepared by the method for preparing the three-dimensional Cu nanowire material with multi-level defects according to any one of claims 1-5.
7. The application of the three-dimensional Cu nanowire material with multi-level defects as described in claim 6 in the electrocatalytic reduction of nitrate or nitrite to ammonia.