Copper-precious metal nano frame material for preparing ammonia through neutral electro-catalysis nitrate reduction as well as preparation method and application of copper-precious metal nano frame material
By loading noble metals onto the surface of copper nanoplates to form a core-shell structured copper-noble metal nanoframework material, the problems of activity and selectivity of copper-based catalysts in neutral media were solved, achieving efficient performance and stability of nitrate reduction to ammonia.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-05
- Publication Date
- 2026-04-03
AI Technical Summary
Existing copper-based catalysts have insufficient nitrate reduction activity and selectivity in neutral media, and traditional methods are insufficient to achieve precise control and nanostructure optimization of noble metals on copper substrates.
Copper nanoplate precursors were synthesized by wet chemical method, and noble metals were loaded onto the surface of copper nanoplates through substitution reaction to form core-shell copper-noble metal nanoframework materials. The degree of noble metal substitution was controlled to optimize electronic structure and interface properties.
It achieves efficient and selective nitrate reduction for ammonia production under neutral conditions, reducing catalyst costs while maintaining catalyst stability and activity.
Smart Images
Figure CN121781183A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrocatalytic materials technology, and particularly relates to a copper-noble metal nanoframework material for neutral electrocatalytic reduction of nitrate to ammonia, its preparation method and application. Background Technology
[0002] Ammonia is an important chemical raw material and a potential clean energy carrier. Currently, industrial ammonia synthesis mainly relies on the high-energy-consuming and high-carbon-emission Haber-Bosch process. Electrocatalytic nitrate reduction to ammonia synthesis is a green pathway to convert water pollution (nitrate) into a high-value product (ammonia) under environmental conditions, but this process requires efficient, stable, and selective electrocatalysts.
[0003] Noble metals (such as Ru, Pt, and Pd) exhibit high intrinsic activity for nitrate reduction, but their high cost and scarcity limit their large-scale application. Copper-based catalysts are less expensive, but their activity and selectivity in neutral media need improvement. Controllable composites of noble metals and copper to construct specific nanostructures represent an effective strategy for balancing catalytic performance and cost.
[0004] Currently, some research has been conducted on copper-noble metal composite catalysts, but how to precisely control the spatial distribution of noble metals on copper substrates, expose specific crystal faces, and form active interfaces that are conducive to reaction mass transfer and intermediate adsorption / desorption remains a technical challenge. Traditional co-reduction or deposition methods often fail to achieve fine control over structure, composition, and interfaces. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention proposes a copper-noble metal nanoframework material for neutral electrocatalytic nitrate reduction to ammonia production, its preparation method, and its application.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] A method for preparing copper-noble metal nanoframework materials for neutral electrocatalytic reduction of nitrate to ammonia includes the following steps:
[0008] (1) Disperse the copper source and structure directing agent in an organic solvent, add a reducing agent and heat to react, and then wash and dry to obtain the copper nanoplate precursor;
[0009] (2) The copper nanoplate precursor is dispersed in an ethanol solution containing noble metal salt for a displacement reaction. The product is washed and dried to obtain a copper-noble metal nanoframework material with a core-shell structure.
[0010] Optionally, the copper source is copper acetate monohydrate Cu(CH3COO)2·H2O;
[0011] The structure directing agent is polyvinylpyrrolidone (PVP).
[0012] The reducing agent is hydrazine hydrate.
[0013] Furthermore, the ratio of the copper source, structure directing agent, and reducing agent is 0.15 mmol: 0.0075 mmol: 90 μL.
[0014] Optionally, in step (1), the heating reaction conditions are: heating to 60 °C and reacting for 30 min.
[0015] Optionally, the drying conditions described in steps (1) and (2) are both: vacuum drying at 60 °C overnight.
[0016] Optionally, the noble metal in the noble metal salt is selected from one or more of Ru, Pt, Pd, or Rh.
[0017] Optionally, the concentration of the ethanol solution containing the noble metal salt is 0.1 mM.
[0018] Optionally, the mass ratio of noble metal to copper in the copper-noble metal nanoframework material is 0.2:10.
[0019] Optionally, the conditions for the displacement reaction are: under an inert atmosphere, at 20-60°C for 0.5 h.
[0020] A copper-noble metal nanoframework material for neutral electrocatalytic reduction of nitrate to ammonia is prepared by the above-described method.
[0021] The application of the above-mentioned copper-noble metal nanoframework materials in the electrocatalytic reduction of nitrate to ammonia in a neutral environment.
[0022] Optionally, the neutral environment refers to a system pH of 6-8.
[0023] Compared with the prior art, the present invention has the following advantages and technical effects:
[0024] (1) Structural advantages: The copper-noble metal nanoframework material prepared by the present invention for neutral electrocatalytic reduction of nitrate to ammonia has a unique three-dimensional nanoframework structure, which provides a huge electrochemical active surface area, abundant active site exposure and excellent reactant / product mass transfer ability.
[0025] (2) Electronic and interface effects: The copper-noble metal nanoframework material disclosed in this invention optimizes the adsorption energy of active sites for nitrate and key reaction intermediates (such as *NO2, *NH2) through the electronic interaction between copper and noble metals, thereby reducing the energy barrier of the rate-determining step of the reaction.
[0026] (3) "Volcano-shaped" performance relationship and optimal solution: In the framework system of the copper-noble metal nanoframework material disclosed in this invention, the performance of nitrate reduction to ammonia (activity and selectivity) and the degree of substitution (noble metal loading / framework porosity) exhibit a "volcano-shaped" curve relationship. Among them, the material with moderate substitution strength achieves the best balance among noble metal utilization efficiency, number of active interfaces, and structural stability, thus achieving optimal performance.
[0027] Shallow displacement: low precious metal loading, insufficient active interface, and poor performance.
[0028] Deep replacement: The frame structure may become too brittle and collapse, and the use of precious metals is uneconomical, resulting in a decline in performance.
[0029] Medium substitution: forms a rich and stable copper-precious metal synergistic interface, maximizes the utilization of precious metal atoms, and achieves peak performance.
[0030] (4) The preparation method is controllable and reproducible: The preparation method of the present invention is simple, and the structure and properties of the final material can be precisely controlled by a single variable (such as concentration), which is easy to scale up for production.
[0031] (5) Balance between cost and performance: This invention uses copper, which is relatively inexpensive, as the main body and only uses a small amount of precious metals for surface modification. While significantly reducing the cost of the catalyst, it achieves performance close to or even exceeding that of pure precious metal catalysts. Attached Figure Description
[0032] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:
[0033] Figure 1 For different Ru 3+ Transmission electron microscopy (TEM) images of nanoframework materials prepared at different concentrations: a and b are copper nanoplates, c and d are low-substituted nanoplates from Example 2, e and f are medium-substituted nanoplates from Example 1, and g and h are high-substituted nanoplates from Example 3.
[0034] Figure 2 Linear sweep voltammetry curves of the materials prepared in Examples 1-3 and Comparative Example 1;
[0035] Figure 3 The diagram shows the Faraday efficiency of ammonia production for the materials prepared in Examples 1-3 and Comparative Example 1.
[0036] Figure 4 The yield curves of ammonia production from the materials prepared in Examples 1-3 and Comparative Example 1 are shown.
[0037] Figure 5Stability testing of the copper-noble metal nanoframework material prepared in Example 1;
[0038] Figure 6 Transmission electron microscopy (TEM) images of the best-performing nanoframework materials prepared for different noble metals: a and b are Cu@2Rh, c and d are Cu@0.8Pd, and e and f are Cu@5Pt.
[0039] Figure 7 The Faraday efficiency graphs for ammonia production of the materials prepared in Example 4 and Comparative Example 1 are shown.
[0040] Figure 8 The yield curves of ammonia production from the materials prepared in Example 4 and Comparative Example 1 are shown.
[0041] Figure 9 The Faraday efficiency graphs for ammonia production of the materials prepared in Example 5 and Comparative Example 1 are shown.
[0042] Figure 10 The yield curves of ammonia production from the materials prepared in Example 5 and Comparative Example 1 are shown.
[0043] Figure 11 The Faraday efficiency graphs for ammonia production of the materials prepared in Example 6 and Comparative Example 1 are shown.
[0044] Figure 12 The yield curves of ammonia production from the materials prepared in Example 6 and Comparative Example 1 are shown. Detailed Implementation
[0045] 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.
[0046] 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. Every smaller range between any stated value or intermediate value within a stated range, and 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] This invention provides an electrocatalyst for the reduction of nitrate to ammonia, which is relatively low in cost, highly active, selective, and stable. Specifically, this invention utilizes a controllable displacement reaction strategy to prepare a series of copper-noble metal nanoframework materials with three-dimensional nanoframework structures. By precisely controlling the degree of displacement, the electronic and geometric structures are optimized, thereby achieving optimal electrocatalytic ammonia synthesis performance under neutral conditions.
[0051] This invention discloses a method for preparing copper-noble metal nanoframework materials, comprising the following steps:
[0052] Step 1: Providing copper nanoplate precursors: A hexagonal copper nanoplate precursor with a specific morphology is synthesized via a wet chemical method; the specific preparation process is as follows:
[0053] 30 mg (0.15 mmol) of copper monohydrate Cu(CH3COO)2·H2O and 300 mg (0.0075 mmol) of polyvinylpyrrolidone (PVP) were dispersed in 15 mL of N,N-dimethylformamide (DMF) and magnetically stirred at 40 °C for 10 min. Then, 90 μL of reducing agent hydrazine hydrate was injected at once, and the temperature was raised to 60 °C and the reaction was continued for 30 min. After the reaction was completed, the sample was washed with deionized water / ethanol by alternating centrifugation and dried under vacuum at 60 °C overnight to obtain a copper nanoplate precursor with uniform particle size, denoted as Cu.
[0054] Step 2: Controlled Displacement Reaction: The copper nanoplate precursor is dispersed in a solution containing a noble metal salt (Ru, but not limited to Ru, and can also be Pt, Pd, Rh), and the displacement reaction is carried out under mild conditions (e.g., room temperature to 60°C, under an inert atmosphere). The specific preparation process is as follows:
[0055] (1) When using the noble metal Ru, the copper nanoplate precursor was immediately redispersed in 10 mL of anhydrous ethanol containing 5 mg (0.000125 mmol) of polyvinylpyrrolidone (PVP). An ethanol solution of RuCl3 was added dropwise under continuous magnetic stirring so that the theoretical mass ratio of Ru to Cu was 0.1:10, 0.2:10 or 0.5:10, respectively. Then, the mixture was stirred at 25 °C in a water bath for 30 min to achieve epitaxial growth of Ru on the Cu surface through in-situ reduction. After the reaction was completed, the mixture was washed again by centrifugation with deionized water / ethanol and dried under vacuum at 60 °C overnight to obtain a Cu@xRu catalyst with a core-shell structure, where x represents the mass ratio of Ru to Cu, and is labeled as Cu@0.1Ru, Cu@0.2Ru or Cu@0.5Ru.
[0056] (2) A method for preparing an extended Cu@xM core-shell structure catalyst, wherein Ru is replaced with Pt, Pd, or Rh, and according to different mass ratios of noble metal M to Cu, the same "ethanol dispersion-water bath at 25 ℃ for 30 min" process conditions as in step (1) above are used to achieve a controllable substitution reaction of the Rh, Pd, or Pt shell. The resulting products are denoted as Cu@xRh, Cu@xPd, or Cu@xPt, where x represents the mass ratio of M to Cu. The specific preparation process is as follows:
[0057] When using the noble metal Rh, copper nanoplatelets were immediately redispersed in 10 mL of anhydrous ethanol containing 5 mg (0.000125 mmol) of polyvinylpyrrolidone (PVP). An ethanol solution of RhCl3 was then added dropwise under continuous magnetic stirring to achieve a theoretical mass ratio of Rh to Cu of 1:15, 2:15, or 3:15. The mixture was then stirred at 25 °C in a water bath for 30 min to achieve epitaxial growth of Rh on the Cu surface through in-situ reduction. After the reaction, the mixture was washed again by centrifugation with deionized water / ethanol and vacuum dried overnight at 60 °C to obtain a core-shell structured Cu@xRh catalyst, where x represents the mass ratio of Rh to Cu, and is labeled as Cu@1Rh, Cu@2Rh, or Cu@3Rh.
[0058] When using the noble metal Pd, the copper nanoplates were immediately redispersed in 10 mL of anhydrous ethanol containing 5 mg (0.000125 mmol) of polyvinylpyrrolidone (PVP). An ethanol solution of PdCl2 was added dropwise under continuous magnetic stirring to achieve a theoretical mass ratio of Pd to Cu of 0.2:10, 0.8:10, or 2.4:10. The mixture was then stirred at 25 °C in a water bath for 30 min to achieve epitaxial growth of Pd on the Cu surface through in-situ reduction. After the reaction, the mixture was washed again by centrifugation with deionized water / ethanol and vacuum dried overnight at 60 °C to obtain a core-shell structured Cu@xPd catalyst, where x represents the mass ratio of Pd to Cu, and is labeled as Cu@0.2Pd, Cu@0.8Pd, or Cu@2.4Pd.
[0059] When using the noble metal Pt, the copper nanoplates were immediately redispersed in 10 mL of anhydrous ethanol containing 5 mg (0.000125 mmol) of polyvinylpyrrolidone (PVP). An ethanol solution of K2PtCl6 was added dropwise under continuous magnetic stirring to achieve a theoretical mass ratio of Pt to Cu of 2.5:20, 5:20, or 10:20. The mixture was then stirred at 25 °C in a water bath for 30 min to achieve epitaxial growth of Pt on the Cu surface through in-situ reduction. After the reaction, the mixture was washed again by centrifugation with deionized water / ethanol and vacuum dried overnight at 60 °C to obtain a core-shell structured Cu@xPt catalyst, where x represents the mass ratio of Pt to Cu, and is labeled as Cu@2.5Pt, Cu@5Pt, or Cu@10Pt.
[0060] This invention defines the control of the aforementioned key parameters, namely, by precisely controlling the displacement reaction conditions (including but not limited to the concentration of noble metal salts, reaction time, and reaction temperature), the degree of noble metal displacement can be continuously and controllably adjusted, thereby obtaining a series of nanoframework structures ranging from "shallow etching" to "deep hollowing." Among these, the concentration of noble metal salts is the core parameter for controlling the displacement intensity. After the reaction is complete, the solid product is separated, washed, and dried to obtain the target copper-noble metal nanoframework material.
[0061] The copper-noble metal nanoframework material prepared by the method of the present invention has a three-dimensional open nanoframework structure, which is composed of interconnected nanoligaments and has abundant pore channels inside the framework.
[0062] This copper-noble metal nanoframework material is a bimetallic system of copper and noble metals. Noble metal atoms are mainly enriched on the surface of the framework, forming an atomically mixed noble metal-rich surface layer or a bimetallic interface with a specific structure. The interior is copper or copper oxide / hydroxide.
[0063] The degree of substitution (or framework hollowness) is a core structural parameter of copper-noble metal nanoframeworks, which is controlled by substitution reaction conditions and directly related to catalytic performance. Materials with a moderate degree of substitution exhibit the best overall performance.
[0064] This invention also discloses the application of the aforementioned copper-noble metal nanoframework material as an electrocatalyst in the nitrate reduction reaction to ammonia. The electrocatalytic reaction is carried out in a neutral (pH = 6-8) nitrate-containing electrolyte solution.
[0065] This copper-noble metal nanoframework material is used to construct the working electrode, which, driven by an electrochemical workstation, efficiently and selectively reduces nitrate to ammonia while suppressing the formation of byproducts (such as nitrogen and nitrite).
[0066] Unless otherwise specified, "room temperature" in this invention refers to 20-30℃.
[0067] All raw materials used in this invention were purchased from the market.
[0068] The technical solution of the present invention will be further illustrated by the following embodiments.
[0069] Example 1: Preparation and Properties of Cu-Ru Nanoframeworks with Moderate (Optimal) Replacement Strength
[0070] Step 1: Synthesize a copper nanoplate precursor with a specific hexagonal morphology using a wet chemical method; the specific preparation process is as follows:
[0071] 30 mg (0.15 mmol) of copper monohydrate Cu(CH3COO)2·H2O and 300 mg (0.0075 mmol) of polyvinylpyrrolidone (PVP) were dispersed in 15 mL of N,N-dimethylformamide (DMF) and magnetically stirred at 40 °C for 10 min. Then, 90 μL of reducing agent hydrazine hydrate was injected at once, and the temperature was raised to 60 °C and the reaction was continued for 30 min. After the reaction was completed, the sample was washed with deionized water / ethanol by alternating centrifugation and dried under vacuum at 60 °C overnight to obtain a copper nanoplate precursor with uniform particle size, denoted as Cu.
[0072] Step 2: Controlled displacement reaction, the specific preparation process is as follows:
[0073] The copper nanoplate precursor was immediately redispersed in 10 mL of anhydrous ethanol containing 5 mg (0.000125 mmol) of polyvinylpyrrolidone (PVP). An ethanol solution of RuCl3 (0.1 mM) was added dropwise under continuous magnetic stirring to achieve a theoretical Ru to Cu mass ratio of 0.2:10. The mixture was then stirred at 25 °C in a water bath for 30 min to achieve epitaxial growth of Ru on the Cu surface through in-situ reduction. After the reaction, the mixture was washed again by centrifugation with deionized water / ethanol and dried under vacuum at 60 °C overnight to obtain a core-shell structure Cu@xRu catalyst, denoted as Cu@0.2Ru.
[0074] Figure 1 In Figures e and f, transmission electron microscopy (TEM) images of the copper-noble metal nanoframework material (medium-concentration replacement) prepared in Example 1 of this invention are shown: As can be seen from the figures, the copper-noble metal nanoframework material prepared in Example 1 forms a complete three-dimensional framework and has abundant Cu-Ru metal interfaces.
[0075] Electrochemical testing: In a 0.1 M K₂SO₄ + 0.1 M KNO₃ (pH=7) electrolyte, at a potential of -0.99 V vs. RHE, the ammonia yield reached 5174.2 μg h⁻¹. -1 mg cat -1 Faraday efficiency is as high as 96%.
[0076] Example 2: Preparation and Properties of Low-Substitution-Strength Cu-Ru Nanoframeworks
[0077] The difference from Example 1 is that the RuCl3 concentration was reduced to 0.05 mM, making the theoretical mass ratio of Ru to Cu 0.1:10. The prepared Cu-Ru nanoframework is denoted as Cu@0.1Ru.
[0078] Figure 1 c and d are transmission electron microscope (TEM) images of the copper-noble metal nanoframework material (low displacement) prepared in Example 2 of this invention: it can be seen from the images that the surface of the nanoplate is only slightly etched and no complete framework is formed.
[0079] Performance: Both ammonia yield and Faraday efficiency were significantly lower than in Example 1.
[0080] Example 3: Preparation and Properties of High-Replacement-Strength Cu-Ru Nanoframeworks
[0081] The difference from Example 1 is that the RuCl3 concentration was increased to 0.25 mM, making the theoretical mass ratio of Ru to Cu 0.5:10. The prepared Cu-Ru nanoframework is denoted as Cu@0.5Ru.
[0082] Figure 1 In the image, g and h are transmission electron microscope (TEM) images of the copper-noble metal nanoframework material (high displacement) prepared in Example 3 of this invention: it can be seen from the image that the framework structure of the material is completely etched.
[0083] Performance: Initial activity may be high, but performance decays rapidly in stability tests, and overall performance is lower than that of Example 1.
[0084] Comparative Example 1: Pure Cu nanoplates were prepared directly using the method in step one of Example 1.
[0085] Performance: Both activity and selectivity are very poor.
[0086] Example 4
[0087] The difference from Example 1 is that in step two, Ru is replaced with Rh. The specific preparation process of the copper-noble metal nanoframework material is as follows:
[0088] Copper nanoplatelets were immediately redispersed in 10 mL of anhydrous ethanol containing 5 mg (0.000125 mmol) of polyvinylpyrrolidone (PVP). An ethanol solution of RhCl3 was added dropwise under continuous magnetic stirring to achieve theoretical Rh to Cu mass ratios of 1:15 (0.024 mM RhCl3 ethanol solution concentration), 2:15 (0.048 mM RhCl3 ethanol solution concentration), or 3:15 (0.072 mM RhCl3 ethanol solution concentration). The mixture was then stirred at 25 °C in a water bath for 30 min to achieve epitaxial growth of Rh on the Cu surface through in-situ reduction. After the reaction, the mixture was washed again by centrifugation with deionized water / ethanol and dried under vacuum at 60 °C overnight to obtain a core-shell structured Cu@xRh catalyst, where x represents the mass ratio of Rh to Cu, and is labeled Cu@1Rh, Cu@2Rh, or Cu@3Rh.
[0089] Example 5
[0090] The difference from Example 1 is that in step two, Ru is replaced with Pd. The specific preparation process of the copper-noble metal nanoframework material is as follows:
[0091] Copper nanoplatelets were immediately redispersed in 10 mL of anhydrous ethanol containing 5 mg (0.000125 mmol) of polyvinylpyrrolidone (PVP). An ethanol solution of PdCl2 was added dropwise under continuous magnetic stirring to achieve a theoretical Pd:Cu mass ratio of 0.2:10 (PdCl2 ethanol solution concentration of 0.0014 mM), 0.8:10 (PdCl2 ethanol solution concentration of 0.0056 mM), or 2.4:10 (PdCl2 ethanol solution concentration of 0.0168 mM). The mixture was then stirred at 25 °C in a water bath for 30 min to achieve epitaxial growth of Pd on the Cu surface through in-situ reduction. After the reaction, the nanoplatelets were washed again by centrifugation with deionized water / ethanol. The catalyst was dried under vacuum overnight at ℃ to obtain a Cu@xPd catalyst with a core-shell structure, where x represents the mass ratio of Pd to Cu, and is labeled as Cu@0.2Pd, Cu@0.8Pd, or Cu@2.4Pd.
[0092] Example 6
[0093] The difference from Example 1 is that in step two, Ru is replaced with Pt. The specific preparation process of the copper-noble metal nanoframework material is as follows:
[0094] Copper nanoplatelets were immediately redispersed in 10 mL of anhydrous ethanol containing 5 mg (0.000125 mmol) of polyvinylpyrrolidone (PVP). An ethanol solution of K₂PtCl₆ was added dropwise under continuous magnetic stirring to achieve theoretical Pt to Cu mass ratios of 2.5:20 (0.001 mM K₂PtCl₆ ethanol solution concentration), 5:20 (0.002 mM K₂PtCl₆ ethanol solution concentration), or 10:20 (0.004 mM K₂PtCl₆ ethanol solution concentration). The mixture was then stirred at 25 °C in a water bath for 30 min to achieve epitaxial growth of Pt on the Cu surface through in-situ reduction. After the reaction, the mixture was washed again by centrifugation with deionized water / ethanol and dried under vacuum at 60 °C overnight to obtain a core-shell structured Cu@xPt catalyst, where x represents the mass ratio of Pt to Cu, and is labeled Cu@2.5Pt, Cu@5Pt, or Cu@10Pt.
[0095] Effect verification
[0096] The copper-noble metal nanoframework material prepared in Example 1 was used for long-term stability testing. The specific test steps and conditions were as follows: In an electrolyte of 0.1 M K2SO4 + 0.1 M KNO3 (pH=7), the catalyst (i.e., the copper-noble metal nanoframework material prepared in Example 1) after CV activation (10 cyclic voltammetric scans in the range of -2V to 2V, with a scan rate of 0.05mV / s) was subjected to an IT test for 300 seconds at a potential of -0.99V vs. RHE, and the performance was evaluated.
[0097] Results: After 20 cycles of continuous electrolysis, the copper-noble metal nanoframework material prepared in Example 1 retained more than 99% of its properties, and TEM showed that the framework structure was basically maintained.
[0098] Figure 2 Linear sweep voltammetry curves of the materials prepared in Examples 1-3 and Comparative Example 1 are shown in the figure. It can be seen from the figure that all samples in the NO3-containing... - All solutions exhibited a clear reduction current response, with a significantly enhanced reduction peak current at Cu@0.2Ru, indicating optimal nitrate reduction activity. (Compared to solutions without NO3...) - The background current of the system can eliminate interference from side reactions such as hydrogen evolution, verifying the presence of NO3. - Reduction to ammonia is the main reaction pathway. Furthermore, the pure Cu sample exhibits extremely low activity, further highlighting the crucial promoting effect of noble metal introduction on catalytic performance. This result is consistent with TEM observations, confirming that the moderately substituted Cu@0.2Ru structure possesses both high activity and stability, representing the optimal catalytic configuration.
[0099] Figure 3 The figures show the Faradaic efficiency of ammonia production from the materials prepared in Examples 1-3 and Comparative Example 1. As can be seen from the figures, the Faradaic efficiency of the pure Cu sample is generally below 50% across the entire potential range, indicating poor selectivity for ammonia production. This result is consistent with the catalytic activity test. However, at -0.99 V vs. RHE, Cu@0.2Ru with a moderate degree of substitution exhibits the optimal electron transfer path and bimetallic synergistic effect, achieving efficient and highly selective ammonia production from nitrate reduction.
[0100] Figure 4 The figures show the ammonia yield curves of the materials prepared in Examples 1-3 and Comparative Example 1. As can be seen from the figures, the ammonia yield of all samples increases with a negative potential shift, with Cu@0.2Ru achieving a yield as high as 6600 μg h⁻¹ at -1.39 V vs. RHE. -1 mg -1The Cu@0.5Ru catalyst showed significantly better catalytic activity than other samples, demonstrating its superior catalytic activity. Although Cu@0.5Ru achieved a higher yield at high potentials, its high noble metal loading and low production cost made it uneconomical. In contrast, the pure Cu sample had an extremely low yield, indicating its poor activity for nitrate reduction. This result is consistent with the Faraday efficiency and LSV curves, further confirming that Cu@0.2Ru with a moderate degree of substitution possesses the optimal electron transport capability and catalytic efficiency, making it an ideal catalyst configuration for achieving efficient nitrate reduction to ammonia.
[0101] Figure 5 The stability test of the copper-noble metal nanoframework material prepared in Example 1 is shown in the figure. As can be seen from the figure, when the material is operated at -0.99V vs. RHE potential, the ammonia Faradaic efficiency remains above 90% with minimal fluctuation, indicating excellent selectivity and resistance to side reactions. Simultaneously, the ammonia yield remains stably maintained at approximately 3800-5300 μg h⁻¹. -1 mg -1 Near the target area, no significant degradation trend was observed, indicating that the catalyst structure is stable and the active sites are well maintained. The overall performance showed high consistency across multiple cycles, demonstrating that this copper-noble metal nanoframework material possesses excellent long-term catalytic stability and is suitable for practical electrochemical nitrate reduction to ammonia production applications.
[0102] Figure 6 Transmission electron microscopy (TEM) images of nanoframework materials prepared with different noble metals: a and b are Cu@2Rh, c and d are Cu@0.8Pd, and e and f are Cu@5Pt. The images show that the surface morphology changes differently after doping with different noble metals. a and b show the epitaxial growth of Rh on the Cu surface, resulting in a "hollowed-out" structure for the copper nanoplate, with only a small amount of Cu present on the surface. c and d show a gentle Pd doping process, with Cu and Pd signals highly overlapping within the plate surface, exhibiting an atomically uniform distribution. e and f show that Pt doping in the copper nanoplate starts from the edge, with the Pt signal first lighting up along the edge and then moving towards the center, clearly outlining an "edge-first, outside-to-inside" doping path.
[0103] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing copper-noble metal nanoframework materials for neutral electrocatalytic nitrate reduction to ammonia, characterized in that, Includes the following steps: (1) Disperse the copper source and structure directing agent in an organic solvent, add a reducing agent and heat to react, and then wash and dry to obtain the copper nanoplate precursor; (2) The copper nanoplate precursor is dispersed in an ethanol solution containing noble metal salt for a displacement reaction. The product is washed and dried to obtain a copper-noble metal nanoframework material with a core-shell structure.
2. The method for preparing a copper-noble metal nanoframework material for neutral electrocatalytic nitrate reduction to ammonia according to claim 1, characterized in that, The copper source is copper acetate monohydrate; The structure directing agent is polyvinylpyrrolidone; The reducing agent is hydrazine hydrate.
3. The method for preparing a copper-noble metal nanoframework material for neutral electrocatalytic nitrate reduction to ammonia according to claim 1, characterized in that, The ratio of copper source, structure directing agent and reducing agent is 0.15 mmol: 0.0075 mmol: 90 μL.
4. The method for preparing a copper-noble metal nanoframework material for neutral electrocatalytic nitrate reduction to ammonia according to claim 1, characterized in that, In step (1), the heating reaction conditions are: heating to 60 °C and reacting for 30 min.
5. The method for preparing a copper-noble metal nanoframework material for neutral electrocatalytic nitrate reduction to ammonia according to claim 1, characterized in that, The drying conditions described in steps (1) and (2) are: vacuum drying at 60 °C overnight.
6. The method for preparing a copper-noble metal nanoframework material for neutral electrocatalytic nitrate reduction to ammonia according to claim 1, characterized in that, The precious metal in the precious metal salt is selected from at least one of Ru, Pt, Pd and Rh.
7. The method for preparing a copper-noble metal nanoframework material for neutral electrocatalytic nitrate reduction to ammonia according to claim 1, characterized in that, The mass ratio of noble metal to copper in the copper-noble metal nanoframework material is 0.2:
10.
8. The method for preparing a copper-noble metal nanoframework material for neutral electrocatalytic nitrate reduction to ammonia according to claim 1, characterized in that, The conditions for the displacement reaction are: reaction at 20-60℃ for 0.5h under an inert atmosphere.
9. A copper-noble metal nanoframework material for neutral electrocatalytic nitrate reduction to ammonia, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.
10. The application of the copper-noble metal nanoframework material as described in claim 9 in the electrocatalytic reduction of nitrate to ammonia in a neutral environment.