Copper-iron bimetallic hierarchical heterostructure catalyst as well as preparation method and application thereof

Abstract

The invention relates to a copper-iron bimetallic hierarchical heterostructure catalyst and a preparation method and application thereof.The preparation method comprises the steps that firstly, a copper source and an iron source are mixed in an alkaline solution, a hydrothermal reaction is conducted, and a precursor is obtained; carrying out reduction treatment and aging treatment on the precursor to obtain an intermediate; and calcining the intermediate to obtain the copper-iron bimetallic hierarchical heterostructure catalyst. Compared with the prior art, through a unique precursor template-thermally induced reconstruction strategy, the prepared graded catalyst is structurally characterized in that a three-dimensional porous framework is constructed by a plurality of mutually connected flaky iron substrates, and copper-rich nanoclusters are loaded on the surface of the framework at high density. The catalyst shows excellent catalytic activity, selectivity and stability at a low potential in a reaction of generating ammonia by electrocatalytic reduction of nitric oxide.

Description

Technical Field

[0001] This invention belongs to the fields of electrocatalytic materials science and environmental catalysis technology, and relates to a copper-iron bimetallic hierarchical heterostructure catalyst, its preparation method and application, especially a catalyst with an interconnected sheet-like iron substrate forming a porous framework and copper nanoclusters enriched on the surface, as well as its preparation method and application in the electrocatalytic reduction of nitric oxide (NO) pollutant into ammonia (NH3), a high-value chemical. Background Technology

[0002] Ammonia (NH3) is a key raw material for maintaining modern agricultural and chemical systems and is considered a highly promising zero-carbon energy carrier. Currently, its large-scale production still relies on the energy-intensive and carbon-emission Haber-Bosch process. Meanwhile, nitrogen oxides (NOx, mainly NO) emitted from industrial flue gas and internal combustion engine exhaust are major pollutants contributing to environmental problems such as acid rain and photochemical smog. Therefore, developing a technology that can utilize pollutant NO under mild conditions to directly electrocatalytically synthesize the high-value-added product NH3—namely, electrocatalytic nitric oxide reduction reaction (eNORR)—not only aligns with the "dual-carbon" strategic goals but also possesses significant environmental and economic value.

[0003] The core bottleneck of eNORR technology lies in developing efficient, stable, and economical electrocatalysts. Copper (Cu)-based materials have attracted widespread attention due to their excellent intrinsic selectivity for the reduction of NO to NH3. However, the activity and yield of single-metal Cu catalysts often fall short of practical application requirements. To overcome this limitation, researchers have attempted to introduce a second metal (such as Fe, Co, Ni, etc.) to construct bimetallic catalysts, hoping to leverage the synergistic effect between different metals to enhance catalytic performance.

[0004] To overcome the performance bottleneck of single-metal catalysts, introducing a second transition metal to construct bimetallic catalysts and utilizing the synergistic effect between different metal components to modulate the surface electronic structure of the catalyst and the adsorption behavior of reaction intermediates has become a widely adopted and effective strategy. Among numerous second metal candidates, iron (Fe) is considered one of the ideal choices for constructing bimetallic eNORR catalysts with copper due to its inherent catalytic activity, abundant reserves on Earth, low cost, and significant electronic interactions with copper. Therefore, the development of high-performance copper-iron bimetallic catalysts has become a research hotspot in this field.

[0005] To maximize the synergistic effect between copper and iron components, the microstructure design of catalysts, especially interface engineering and morphology control, has become the core of current research. Researchers are actively exploring advanced structures that go beyond traditional mixing or alloying, such as hierarchical porous structures with high specific surface area and ordered mass transfer channels.

[0006] Among many advanced synthetic strategies, using inorganic compounds with specific morphologies as self-sacrificing templates to construct complex metals or composite materials through subsequent in-situ chemical transformations is a promising "bottom-up" synthetic approach. This approach offers the possibility of precisely constructing catalysts with specific spatial configurations.

[0007] However, the application of this concept to copper-iron bimetallic catalyst systems, particularly exploring how to utilize plate-like copper-iron oxides as precursor templates and guide thermodynamically driven ordered reconstruction of components through a mild and controllable transformation pathway to obtain a specific hierarchical heterostructure of "copper-rich clusters supported on an iron-based porous framework," is rarely reported in existing published technical literature, leaving a significant technological gap. Therefore, there remains a technical need in this field to develop a novel preparation method that can overcome the limitations of traditional preparation strategies, constructing a novel copper-iron hierarchical catalyst with well-defined structures, clear interfaces, and excellent performance in a "bottom-up" and "template-guided" manner to meet the growing demand for efficient eNORR technology. Summary of the Invention

[0008] The purpose of this invention is to provide a novel, high-performance copper-iron bimetallic hierarchical heterostructure catalyst, its preparation method, and its application, to solve the problem of efficient electrocatalytic synthesis of ammonia from low-concentration NO in a GDE system.

[0009] The objective of this invention can be achieved through the following technical solutions: The first aspect of this invention provides a method for preparing a copper-iron bimetallic hierarchical heterostructure catalyst, comprising the following steps: S1: The copper source and iron source are mixed in an alkaline solution and subjected to a hydrothermal reaction to obtain a copper-iron composite oxide precursor with a nanosheet morphology. S2: The precursor is reduced and aged to obtain a metallized intermediate that maintains the morphology and contour of the nanosheets; S3: The intermediate is calcined to promote component reconstruction and obtain a copper-iron bimetallic hierarchical heterostructure catalyst.

[0010] In some specific embodiments, in step S1, the copper source is selected from cuprous iodide, the iron source is selected from ferric chloride, and the alkali in the alkaline solution is selected from potassium hydroxide.

[0011] In some specific embodiments, in step S1, the molar ratio of the copper source, iron source, and alkali is (1~3):(1~3):(70~75). Preferably, the molar ratio between copper in the copper source and iron in the iron source is 1:1.

[0012] In some specific embodiments, in step S1, the hydrothermal reaction is carried out at a temperature of 120-140 °C for 6-8 h.

[0013] In some specific embodiments, the precursor is CuFeO2 having a Delaunay crystal phase.

[0014] In some specific embodiments, in step S2, the reduction treatment uses an aqueous solution of ethylene glycol as the solvent, a treatment temperature of 0-5°C, a treatment atmosphere of nitrogen, and NaBH4 as the reducing agent. The ratio of the molar amount of the reducing agent to the total molar amount of copper in the copper source and iron in the iron source is 8-9:1. The pH is 11-12, and the treatment time is 20-40 min.

[0015] In some specific embodiments, the NaBH4 is added dropwise to the dispersion containing the precursor at a dropping rate of 0.5 to 1.5 mL / min.

[0016] In some specific implementations, in step S2, the aging process is carried out at room temperature for 20 to 40 minutes.

[0017] In some specific embodiments, in step S3, the calcination temperature is 400~500 ℃, the calcination time is 0.5~2 h, the heating rate is preferably 2~5 ℃ / min, and the calcination atmosphere is an inert gas.

[0018] A second aspect of the present invention provides a copper-iron bimetallic hierarchical heterostructure catalyst, prepared by the method described above. The structure of the copper-iron bimetallic hierarchical heterostructure catalyst is as follows: a three-dimensional porous framework is formed by multiple interconnected sheet-like iron substrates, and the surface of the framework is enriched with copper.

[0019] A third aspect of the present invention provides an application of the copper-iron bimetallic hierarchical heterostructure catalyst as described above, including using the copper-iron bimetallic hierarchical heterostructure catalyst as a catalyst for a gas diffusion electrode in an electrocatalytic NO reduction reaction.

[0020] In some specific embodiments, the electrolyte used in the electrocatalytic NO reduction reaction is a 0.5~1 M Na2SO4 solution.

[0021] This invention employs a unique "precursor template-thermally induced reconstruction" strategy to construct a hierarchical catalyst with synergistic enhancement of physical mass transfer and chemical activation. Its core structural feature lies in the in-situ construction of a three-dimensionally interconnected porous conductive framework from multiple interconnected sheet-like iron substrates. This framework effectively shortens the diffusion path of reactant gases and enhances charge transport. Simultaneously, high-density copper-rich nanoclusters loaded on the surface of this framework not only maximize the exposed area of ​​active sites through geometric effects but also effectively suppress competitive hydrogen evolution side reactions by regulating the electronic structure through a tight Fe-Cu heterostructure. Benefiting from the improved mass transfer due to this hierarchical porous structure and the optimized reaction kinetics through the bimetallic interface, this catalyst exhibits excellent catalytic activity, selectivity, and stability at low potentials in the electrocatalytic reduction of nitric oxide to ammonia.

[0022] Specifically, in existing technologies, catalyst particles often tend to densely pack together, preventing the already low-solubility nitric oxide (NO) from reaching the catalyst interior. In this invention, interconnected sheet-like iron substrates form a three-dimensional porous framework, effectively solving the gas-liquid mass transfer problem. This open framework directly leads to the formation of hierarchical pores (macropores-mesopores-micropores), which is essentially a hierarchical pore network. This effectively shortens the path length for NO molecules to diffuse from the bulk electrolyte to the deeper layers of the catalyst, making it particularly suitable for simulating low-concentration NO feed conditions in industrial waste gas.

[0023] In traditional copper-iron alloys, a large number of active copper atoms are embedded inside the crystal lattice and cannot participate in the reaction, leading to problems such as agglomeration of active components and low utilization. In this invention, a "precursor template-thermal remodeling" strategy is employed to enable copper-rich components to be loaded in the form of "nanoclusters" with high dispersion and high density on the surface of an iron substrate. From a geometric perspective, this effectively increases the electrochemically active surface area (ECSA) of the catalyst. Furthermore, since the copper clusters are grown in situ on the iron substrate, the iron substrate provides a strong physical and chemical anchoring effect on the copper clusters, preventing the agglomeration and loss of copper particles during long-term electrolysis.

[0024] Simple physical mixing cannot change the nature of the catalyst. In this application, a tight Cu-Fe heterostructure formed through thermally induced reconstruction modulates the electronic structure of the active center at the atomic scale. Iron, as the substrate, modulates the electron cloud density of the surface copper clusters (charge transfer from Fe to Cu) through interfacial electron transfer. This modulation effectively weakens the adsorption capacity of hydrogen protons (H) at the copper sites, thereby suppressing the hydrogen evolution reaction (HER). Furthermore, Fe itself is oxyphilic; at the interface, the Fe substrate may assist in the adsorption of the oxygen terminus of NO molecules, while the Cu clusters adsorb the nitrogen terminus. This "dual-site synergistic" mode greatly reduces the energy barrier (rate-limiting step) for NO bond breaking, thus achieving high conversion efficiency at low potentials.

[0025] Compared with the prior art, the present invention has the following beneficial effects: 1) The preparation method is novel and highly controllable. The "precursor template-thermal remodeling" synthesis strategy proposed in this invention utilizes the inherent physicochemical differences between components to drive the ordered rearrangement of the catalyst's microstructure through a simple two-step method. Compared to traditional methods such as physical mixing, this invention's method can construct a tight Cu-Fe heterostructure in situ, laying the structural foundation for achieving efficient bimetallic synergistic catalysis. 2) The catalyst has a unique structure and ingenious design. The catalyst prepared by this invention has a unique hierarchical heterogeneous structure of "clusters on a plate". The three-dimensional porous framework composed of interconnected sheet-like iron substrates provides stable physical support and excellent mass transfer channels for the catalyst; while the copper-rich nanoclusters highly dispersed on the surface of the iron substrate maximize the exposure of Cu-Fe interfacial active sites, achieving an effective unity of structure and function; 3) Excellent catalytic performance and promising application prospects. In the gaseous diffusion electrode (GDE) test system, which is closer to practical applications, the catalyst prepared in this invention exhibits excellent performance for the eNORR reaction, achieving high ammonia yield and high Faradaic efficiency at low potentials, and demonstrating good operational stability. This provides a valuable technical approach and a promising candidate material for the subsequent development of efficient eNORR catalysts for industrial waste gas treatment and resource utilization. Attached Figure Description

[0026] Figure 1 The morphology and elemental distribution of the catalyst prepared in Example 1 of this invention at different stages are shown in the diagram; wherein, Figure 1 (a) is a SEM image of the precursor CuFeO2 nanosheets; Figure 1 (b) is a SEM image of the copper-iron graded catalyst; Figure 1 (c) SEM image of the region used for energy dispersive X-ray spectroscopy (EDS) analysis; Figure 1 (d) is Figure 1 (c) shows the copper element distribution map of the region. Figure 1 (e) is Figure 1 (c) shows the iron distribution in the region.

[0027] Figure 2 The diagram shows the phase structure of the catalyst prepared in Example 1 of this invention at different stages; wherein, Figure 2 (a) is the X-ray diffraction (XRD) pattern of the precursor CuFeO2; Figure 2 (b) shows the XRD pattern of the copper-iron catalyst.

[0028] Figure 3The graph shows the electrocatalytic NO reduction performance of the copper-iron catalyst prepared in Example 1 of this invention at different potentials.

[0029] Figure 4 This is a graph showing the long-term stability test of the copper-iron catalyst prepared in Example 1 of the present invention.

[0030] Figure 5 This is a performance comparison diagram of the copper-iron catalyst prepared in Example 1 of the present invention and the catalysts prepared in Comparative Examples 1 to 5.

[0031] Figure 6 The graph shows a performance comparison of catalysts with different Cu / Fe molar ratios prepared in Examples 2-5 of this invention. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0033] The following are more detailed implementation examples, which further illustrate the technical solution of the present invention and the technical effects that can be obtained.

[0034] In the following embodiments, unless otherwise specified, the raw materials, reagents or processing techniques are all conventional commercial products or conventional processing techniques in the art.

[0035] Example 1: Preparation of a staged catalyst (In this invention, Cu / Fe = 1:1) (1) Preparation of CuFeO2 nanosheet precursor: 35.0 mL of deionized water was bubbled with nitrogen for 30 min to remove oxygen, and then 1.428 g CuI (0.0075 mol) and 2.027 g FeCl3·6H2O (0.0075 mol) were added and stirred until completely dissolved. Under ice bath conditions, 30.861 g KOH (0.55 mol) solid was added rapidly in 3-4 portions and stirred for 15 min. The resulting suspension was transferred to a 100 mL polytetrafluoroethylene-lined reactor and reacted at 120 ℃ for 6 h. After the reaction was completed, the mixture was naturally cooled, the product was centrifuged, washed with deionized water until the pH value was about 7, washed 1-2 times with anhydrous ethanol, and finally vacuum dried at 80 ℃ overnight to obtain the CuFeO2 nanosheet precursor.

[0036] (2) Chemical reduction: The precursor obtained in step (1) was dispersed in 50.0 mL of deoxygenated ethylene glycol / water (volume ratio 1:1) mixed solvent and placed in an ice bath at 0-5 °C. The mixture was stirred at a rate of not less than 800 rpm under nitrogen protection. NaBH4 alkaline solution (20 mg / mL) was added dropwise at 0.8 mL / min using a syringe pump. During the addition, a small amount of 4.0 mg / mL NaOH alkaline stabilizer was added to maintain the pH of the reaction system at 11-12 throughout the process. After the addition was completed, stirring was continued for 30 min, and then the ice bath was removed. The mixture was aged at room temperature for 30 min.

[0037] (3) Washing and drying: The product obtained in step (2) was centrifuged under nitrogen protection. Each washing cycle used 30 mL of deoxygenated water and 30 mL of anhydrous ethanol, for a total of 3 cycles. The washed solid was dried under nitrogen at 40-50 °C until it was free-flowing.

[0038] (4) Thermally induced reconstruction: The dried powder obtained in step (3) was thinly spread into a sample layer with a thickness of 3-5 mm in a quartz boat and placed in the constant temperature zone of a tube furnace. First, the air was purged and replaced with argon gas at a flow rate of 300-500 sccm for more than 20 min, and then the argon gas flow rate was stabilized at 150-200 sccm. The furnace temperature was raised to 450 ℃ at a heating rate of 2-3 ℃ / min and held at this temperature for 1 h. After the holding period, the sample was naturally cooled to below 80 ℃ under continuous argon protection, and the sample was removed to obtain the final graded catalyst, denoted as Cat-1.

[0039] Comparative Example 1: Precursor Catalyst The CuFeO2 nanosheet precursor prepared in step (1) of Example 1 was directly used as a catalyst and denoted as Cat-2.

[0040] Comparative Example 2: Untreated intermediate Following the first half of steps (1) and (2) of Example 1, after chemical reduction and washing and drying, without performing the thermally induced reconstruction step, an intermediate product was obtained, denoted as Cat-3.

[0041] Comparative Example 3: Pure Copper Catalyst In step (1) of Example 1, FeCl3·6H2O was not added, and the remaining operating conditions and steps were exactly the same as in Example 1, resulting in a pure copper catalyst, denoted as Cat-4.

[0042] Comparative Example 4: Pure Iron Catalyst In step (1) of Example 1, CuI was not added, and the remaining operating conditions and steps were exactly the same as in Example 1, resulting in a pure iron catalyst, denoted as Cat-5.

[0043] Comparative Example 5: Physically Mixed Catalysts Commercial Cu powder and Fe powder were physically mixed in a 1:1 molar ratio to obtain a catalyst, denoted as Cat-6.

[0044] Examples 2-5: Preparation of catalysts with different Cu / Fe molar ratios The dried CuFeO2 nanosheet powder obtained in step (1) of Example 1 was used as the structural precursor. The structural precursor was added to a N2-deoxygenated deionized water / anhydrous ethanol mixed solvent (volume ratio 1:1) and stirred and dispersed uniformly under N2 protection. According to the target Cu / Fe molar ratio, a calculated amount of cuprous iodide or ferric chloride was added, and stirring was continued for 45 min to form a uniform slurry; then it was slowly evaporated at 60–70 °C and dried to constant weight at 80 °C under N2 atmosphere to obtain the CuFeO2 basis ratio precursor with Cu / Fe molar ratio modulation. The CuFeO2 basis ratio precursor obtained in this step was used to replace the precursor in step (2) of Example 1, and the other operating conditions remained unchanged. Chemical reduction, washing and drying and thermal reconstruction treatment were performed according to steps (2), (3) and (4) of Example 1 to obtain the corresponding graded catalyst.

[0045] Example 2: Preparation of a catalyst with a Cu / Fe molar ratio of 3:1, denoted as Cat-7.

[0046] Example 3: Preparation of a catalyst with a Cu / Fe molar ratio of 2:1, denoted as Cat-8.

[0047] Example 4: Preparation of a catalyst with a Cu / Fe molar ratio of 1:2, denoted as Cat-9.

[0048] Example 5: Preparation of a catalyst with a Cu / Fe molar ratio of 1:3, denoted as Cat-10.

[0049] Test Example 1: Structural Characterization and Performance Evaluation of Catalysts (1) Structural characterization: The CuFeO2 nanosheet precursor and the copper-iron catalyst prepared in Example 1 were structurally characterized. Figure 1 As shown in (a) and 2(a), the precursor is CuFeO2 nanosheets with pure phase and regular morphology. After treatment by the method described in Example 1, as... Figure 1 As shown in (b), the copper-iron catalyst Cat-1 exhibits a hierarchical structure consisting of a sheet-like substrate and coral-like clusters growing on it. Figure 2 As shown in (b), the phases have completely transformed into metallic Cu and metallic Fe. To further determine the elemental distribution, EDS analysis was performed on Cat-1, and the results are as follows: Figure 1 As shown in (c)~1(e). From the figure, it can be seen that the iron element signal ( Figure 1(e) is uniformly distributed on the sheet-like substrate, while the copper element signal ( Figure 1 (d) shows that the clusters on the surface are significantly enriched, confirming that the catalyst prepared in this invention has a unique structure of "copper-rich clusters on an iron-based framework supported on the surface".

[0050] (2) Evaluation of electrocatalytic performance: The catalysts (i.e., Cat-1 to Cat-10) prepared in Examples 1-5 and Comparative Examples 1-5 were respectively made into gas diffusion electrodes and tested in a custom flow cell using a standard three-electrode system.

[0051] Working electrode preparation: 10 mg of catalyst powder was dispersed in a mixed solvent consisting of 960 μL isopropanol and 40 μL Nafion solution (5 wt%), and ultrasonicated for 30 min to form a uniform ink. The ink was then uniformly drop-coated onto the gas diffusion layer (carbon paper), with the catalyst loading controlled at 3 mg / cm³. 2 After being vacuum dried overnight, it is used as the working electrode.

[0052] Test setup: Ag / AgCl was used as the reference electrode, and Pt was used as the counter electrode. The cathode and anode chambers were separated by a Nafion 117 ion exchange membrane.

[0053] Electrolysis conditions: The electrolyte was a 0.5 M Na₂SO₄ solution (pH ≈ 7), which was circulated into the cathode and anode chambers using a peristaltic pump at a rate of 0.5 mL / min. The reaction gas was 3 vol% NO balanced argon gas (3% NO / Ar), and the gas flow rate was controlled at 20 mL / min.

[0054] Data Acquisition and Detection: Linear sweep voltammetry (LSV) and chronoamperometry (it) were performed on an electrochemical workstation. The liquid-phase product (NH3) after the reaction was quantitatively detected by salicylic acid spectrophotometry. This method was modified according to the Chinese National Environmental Protection Standard "Determination of Ammonia Nitrogen in Water - Salicylic Acid Spectrophotometric Method" (HJ 536-2009). The specific detection steps were as follows: 0.1 mL of the electrolyte sample after the reaction was taken and diluted to 10 mL with deionized water (100-fold dilution); then 1 mL of salicylic acid-potassium sodium tartrate solution (color reagent), 100 μL of sodium nitrosoferricyanide solution (catalyst), and 50 μL of sodium hypochlorite solution (oxidant) were added sequentially; after mixing thoroughly, the mixture was allowed to stand at room temperature in the dark for 1 h for color development. The absorbance was measured at 697 nm using a UV-Vis spectrophotometer, and the ammonia concentration in the sample was calculated by combining the concentration-absorbance standard curve plotted using the same color development steps. All potentials were calibrated for a reversible hydrogen electrode (RHE).

[0055] Performance evaluation: such as Figure 3 and Figure 4 As shown, the catalyst Cat-1 of this invention exhibits excellent catalytic performance and stability. At -0.2 V vs. RHE potential, it maintains a Faraday efficiency of 90% and operates stably for over 12 hours. To demonstrate the superiority of the method and structure of this invention, the performance of various catalysts at -0.2 V vs. RHE potential was compared, and the results are as follows: Figure 5 As shown. By Figure 5 It is evident that the performance of the catalyst Cat-1 of this invention is significantly superior to that of the precursor (Cat-2), the untreated intermediate (Cat-3), the pure copper catalyst (Cat-4), the pure iron catalyst (Cat-5), and the physically mixed sample (Cat-6). This comparative result strongly demonstrates the necessity of each step in the method of this invention and the synergistic effect produced by the unique Cu-Fe heterostructure formed by this method. Furthermore, performance tests were conducted on catalysts prepared in Examples 1 and 2-5 with different molar ratios (i.e., Cat-1, Cat-7 to Cat-10), and the results are as follows... Figure 6 As shown. By Figure 6 It was found that, within the tested molar ratio range, the catalyst with a Cu / Fe molar ratio of 2:1 (Cat-8) exhibited the highest catalytic activity. This result demonstrates that the performance of the catalyst of this invention can be optimized by adjusting the ratio of copper to iron components.

[0056] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a copper-iron bimetallic hierarchical heterostructure catalyst, characterized in that, The method includes the following steps: S1: The copper source and iron source are mixed in an alkaline solution and subjected to a hydrothermal reaction to obtain the precursor; S2: The precursor is reduced and aged to obtain the intermediate; S3: The intermediate is calcined to obtain a copper-iron bimetallic hierarchical heterostructure catalyst.

2. The method for preparing the copper-iron bimetallic hierarchical heterostructure catalyst according to claim 1, characterized in that, In step S1, the copper source is selected from cuprous iodide, the iron source is selected from ferric chloride, and the alkali in the alkaline solution is selected from potassium hydroxide.

3. The method for preparing the copper-iron bimetallic hierarchical heterostructure catalyst according to claim 2, characterized in that, In step S1, the molar ratio of the copper source, iron source, and alkali is (1~3):(1~3):(70~75).

4. The method for preparing the copper-iron bimetallic hierarchical heterostructure catalyst according to claim 1, characterized in that, In step S1, the hydrothermal reaction is carried out at a temperature of 120-140 °C for 6-8 h.

5. The method for preparing the copper-iron bimetallic hierarchical heterostructure catalyst according to claim 1, characterized in that, In step S2, the reduction treatment uses an aqueous solution of ethylene glycol as the solvent, a treatment temperature of 0-5 °C, a treatment atmosphere of nitrogen, and NaBH4 as the reducing agent. The ratio of the molar amount of the reducing agent to the total molar amount of copper in the copper source and iron in the iron source is 8-9:

1. The pH is 11-12, and the treatment time is 20-40 min.

6. The method for preparing the copper-iron bimetallic hierarchical heterostructure catalyst according to claim 1, characterized in that, In step S2, the aging process is carried out at room temperature for 20-40 minutes.

7. The method for preparing the copper-iron bimetallic hierarchical heterostructure catalyst according to claim 1, characterized in that, In step S3, the calcination process involves a calcination temperature of 400-500 °C, a calcination time of 0.5-2 h, and an inert gas atmosphere.

8. A copper-iron bimetallic hierarchical heterostructure catalyst, characterized in that, It is prepared by the method described in any one of claims 1 to 7.

9. The application of the copper-iron bimetallic hierarchical heterostructure catalyst as described in claim 8, characterized in that, The copper-iron bimetallic hierarchical heterostructure catalyst is used as a catalyst in the gas diffusion electrode for the electrocatalytic reduction of NO.

10. The application of the copper-iron bimetallic hierarchical heterostructure catalyst according to claim 9, characterized in that, In the electrocatalytic NO reduction reaction, the electrolyte used is a 0.5~1 M Na2SO4 solution.

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