A preparation method of a 3D printed copper nanowire electrode for electrocatalytic reduction of nitrate to synthesize ammonia

Abstract

The application discloses a preparation method of a 3D printing copper nanowire electrode for electrocatalytic reduction of nitrate to synthesize ammonia, which comprises the following steps: firstly, using a high-temperature-resistant resin as a substrate raw material, printing the electrode by using a micro-nano 3D printer; and secondly, sequentially performing chemical plating, chemical oxidation and chemical reduction on the electrode to obtain the 3D printing copper nanowire electrode. The 3D printing copper nanowire electrode prepared by the method has a large amount of hierarchical porous structure, so that the electrode has the advantages of higher specific surface area, porosity and the like, more active sites are provided for a nitrate reduction ammonia synthesis catalyst, and the mass transfer capacity can be effectively improved. The preparation method has the characteristics of simple preparation and controllable structure, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the technical field of electrocatalytic nitrate reduction to ammonia synthesis and the preparation of 3D printed nanowire electrodes, specifically relating to a method for preparing a 3D printed copper nanowire electrode for electrocatalytic nitrate reduction to ammonia synthesis. Background Technology

[0002] Ammonia is not only a fundamental molecule for sustaining life, but also for industrial and energy-related applications. Its annual production is increasing year by year, making it one of the largest synthetic chemicals and highlighting its importance to global economic development. Most ammonia is produced using the well-known Haber-Bosch process, which is based on the combination of hydrogen and nitrogen under high pressure (100 atm) and high temperature (700 K). These specific requirements make the Haber-Bosch process an energy-intensive industrial process, consuming approximately 2% of global energy output. Furthermore, most of the H2 used in the Haber-Bosch process comes from steam methane reforming and water-gas shift reactions, resulting in the emission of greenhouse gases as CO2. Therefore, there is an urgent need for alternative methods to produce ammonia with a less environmentally impactful effect.

[0003] Given my country's status as a major agricultural country, the increased use of nitrogen fertilizers has made nitrates one of the main pollutants in groundwater. The U.S. National Academy of Engineering has identified nitrogen cycle management as a significant challenge, and treating accumulated nitrates in groundwater can mitigate the impact of human activities on the nitrogen cycle. Various treatment methods, including physical, biological, and chemical approaches, have been extensively studied. Electrocatalytic nitrate reduction (NO3RR) is a promising method with advantages such as the availability of renewable electricity as an energy source and the absence of secondary pollution. Furthermore, compared to traditional thermocatalytic nitrate reduction, NO3RR requires only electrons for reduction and does not require the supply of H2 or other reducing agents. The reaction products of NO3RR include N2, NH3, NO, N2O, and NH2OH.

[0004] Recent studies have reported on NO3. – To NH4 +Electrochemical conversion (especially from nitrate-rich waste streams) holds promise for alleviating the need for NH3 production via the energy-intensive Haber-Bosch process. Electrochemical nitrate reduction to ammonia (NRA) not only helps address environmental issues but also reduces energy consumption in ammonia production. The NRA reaction is a complex process facing two main challenges: thermodynamically, the generation of large quantities of intermediates within the desired potential window, and the high overpotential that leads to competition for hydrogen evolution with the active site. To address these challenges, a fundamental understanding of electrochemical NRA is essential to guide the design of highly efficient electrocatalysts. Since nitrate reduction is a surface-sensitive reaction, suitable electrocatalysts are crucial. Controlling the structure and composition of the electrode surface is vital for achieving better electrocatalyst performance. Surface engineering techniques allow for the customization of the electrode's surface composition and structure to improve the catalytic efficiency and stability of the electrocatalyst.

[0005] In recent years, 3D printing technology, as an emerging material and device fabrication technology, has attracted much attention due to its potential applications in electronics, aerospace, medicine, and new energy fields. Advances in 3D printing technology (also known as additive manufacturing) have revolutionized materials manufacturing, offering rapid prototyping capabilities and flexibility in design and printing. This innovative technology has the potential to provide catalyst structures with diverse geometries, better rigidity, and adjustable porosity and size, effectively alleviating many limitations associated with traditional manufacturing techniques. Furthermore, designs can be modified relatively easily using computer-aided design (CAD) software. These 3D-printed catalyst structures, with their micrometer (μm) resolution, can induce pores and increase specific surface area, providing nanoscale features that enhance catalytic activity. Simultaneously, 3D-printed catalyst structures can be designed with different geometries, increasing the opportunities to fabricate active catalyst structures for the reduction of nitrates to ammonia.

[0006] Currently, many metals have been explored for use in the electrocatalytic reduction of nitrate to ammonia. Among them, copper, whether alone or in combination with other metals, has shown excellent electrocatalytic reduction performance of nitrate. Based on this, this invention presents a 3D-printed copper nanowire electrode prepared by 3D printing technology, chemical plating, oxidation and reduction treatment for use in the electrocatalytic reduction of nitrate to ammonia. There are currently no related reports in this area. Summary of the Invention

[0007] The technical problem solved by this invention is to provide a method for preparing a 3D-printed copper nanowire electrode for electrocatalytic reduction of nitrate to ammonia. This method successfully prepares a 3D-printed copper nanowire electrode through steps such as 3D printing, chemical plating, oxidation, and heating reduction. The prepared 3D-printed copper nanowire electrode exhibits excellent activity and stability in the electrocatalytic reduction of nitrate to ammonia.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preparing a 3D-printed copper nanowire electrode for electrocatalytic reduction of nitrate to ammonia, characterized by the following specific process:

[0009] Step S1: Design the electrode structure model using 3D modeling software. The electrode is an ordered porous array structure composed of 10×10 basic units, each basic unit being 0.1cm×0.1cm×0.1cm, with an overall size of 1cm×1cm×0.1cm and a porosity of 92%.

[0010] Step S2: Export the electrode structure model designed in Step S1 as an STL file, and then slice the STL file with a layer thickness of 10μm to obtain a series of two-dimensional images of the electrode structure.

[0011] Step S3: Import the two-dimensional image of the electrode structure processed in step S2 into the micro-nano 3D printer, adjust the printing platform, set the printing parameters, start printing the electrode, take out the printed electrode, rinse it with ethanol, and then cure it in the UV curing oven for 2 minutes to obtain the 3D printed electrode.

[0012] Step S4: The 3D printed electrode obtained in step S3 is subjected to chemical plating pretreatment by immersing it in a mixed solution of KMnO4 and KOH, rinsing it with deionized water, then immersing it in Na2S2O3 solution, rinsing it with deionized water and drying it, and finally immersing it in a mixed solution of AgNO3 and ethanol to obtain the chemically pretreated 3D printed electrode.

[0013] Step S5: The 3D printed electrode obtained from the pre-treatment in step S4 is subjected to electroless copper plating in a solution containing NaOH, CuSO4·5H2O, HCHO, and C. 10 H 14 N₂Na₂O₈, NaKC₄H₄O₆, C 10 The 3D-printed electrode was obtained by immersing in a solution of H8N2 and K4Fe(CN)6 and then vacuum drying.

[0014] Step S6: The chemically plated copper 3D printed electrode obtained in step S5 is subjected to oxidation treatment by immersing it in a solution containing (NH4)2S2O8 and NaOH to obtain a chemically plated copper and oxidized 3D printed electrode.

[0015] Step S7: The chemically plated and oxidized 3D printed electrode obtained in step S6 is subjected to a heat reduction treatment to obtain a 3D printed copper nanowire electrode.

[0016] Further specifying, the micro-nano 3D printer mentioned in step S3 is the microArch S240 from Mofang Precision, which has an optical precision of 10μm and a printing layer thickness of 10-40μm.

[0017] Further specifying, in step S4, the pretreatment for chemical plating involves immersion at 40°C for 2 minutes in a solution of 7.5 g / L KMnO4 and 20 g / L KOH; immersion at 60°C for 10 minutes in a solution of 5 g / L Na2S2O3; drying at 40°C for 30 minutes; and immersion at 25°C for 10 minutes in a solution of 2 g / L AgNO3 and 50 mL / L ethanol.

[0018] Further specifying, the conditions for electroless copper plating in step S5 are: NaOH 10g / L, CuSO4·5H2O 8g / L, HCHO 12mL / L, C 10 H 14 N2Na2O8 2g / L, NaKC4H4O6 2g / L, C 10 The sample was soaked in a solution of 10 mg / L H8N2 and 20 mg / L K4Fe(CN)6 at 45°C for 40 minutes, and then vacuum dried at 60°C for 6 hours.

[0019] Further specifying, the oxidation treatment conditions in step S6 are: soaking in 0.1 mol / L (NH4)2S2O8 and 1 mol / L NaOH solution for 1 hour, followed by vacuum drying at 60°C for 6 hours.

[0020] Further specifying, the heating and reduction treatment in step S7 is performed by heating at 300°C for 1 hour in a tube furnace, with a hydrogen-argon mixture in the heating and reduction atmosphere.

[0021] The method for preparing a 3D-printed copper nanowire electrode for electrocatalytic reduction of nitrate to ammonia, as described in this invention, is characterized by the following specific steps:

[0022] Step S1: Design the electrode structure model using 3D modeling software. The electrode is an ordered porous array structure composed of 10×10 basic units, each basic unit being 0.1cm×0.1cm×0.1cm, with an overall size of 1cm×1cm×0.1cm and a porosity of 92%.

[0023] Step S2: Export the electrode structure model designed in Step S1 as an STL file, and then slice the STL file with a layer thickness of 10μm to obtain a series of two-dimensional images of the electrode structure.

[0024] Step S3: Import the two-dimensional image of the electrode structure processed in step S2 into the micro-nano 3D printer, adjust the printing platform, set the printing parameters, start printing the electrode, take out the printed electrode, rinse with ethanol, and then cure in the UV curing chamber for 2 minutes to obtain the 3D printed electrode. The micro-nano 3D printer is the microArch S240 of Mofang Precision. The optical precision of the micro-nano 3D printer is 10μm, and the printing layer thickness is 10μm.

[0025] Step S4: The 3D printed electrode obtained in step S3 is immersed in a solution of KMnO4 7.5 g / L and KOH 20 g / L at 40°C for 2 minutes; immersed in a solution of Na2S2O3 5 g / L at 60°C for 10 minutes; dried at 40°C for 30 minutes; and immersed in a solution of AgNO3 2 g / L and ethanol 50 mL / L at 25°C for 10 minutes to obtain a 3D printed electrode pretreated with electroless plating.

[0026] Step S5: The 3D printed electrode obtained from the pre-chemical plating treatment in step S4 is subjected to NaOH 10g / L, CuSO4·5H2O 8g / L, HCHO 12mL / L, C 10 H 14 N2Na2O8 2g / L, NaKC4H4O6 2g / L, C 10 The electrode was immersed in a solution of 10 mg / L H8N2 and 20 mg / L K4Fe(CN)6 at 45°C for 40 minutes, and then dried at 60°C for 6 hours to obtain a chemically plated copper 3D printed electrode.

[0027] Step S6: Immerse the chemically plated copper 3D printed electrode obtained in step S5 in 0.1 mol / L (NH4)2S2O8 and 1 mol / L NaOH solution for 1 hour, and then vacuum dry at 60℃ for 6 hours to obtain a chemically plated copper and oxidized 3D printed electrode.

[0028] Step S7: Place the chemically plated and oxidized 3D printed electrode obtained in step S6 in a tube furnace and heat it at 300°C for 1 hour under a hydrogen-argon mixed gas to obtain a 3D printed copper nanowire electrode.

[0029] This 3D-printed copper nanowire electrode provides more active sites for the electrocatalytic NRA reaction and allows for sufficient contact with the electrolyte, which is beneficial for mass transfer of reactants on the catalyst surface. The 3D-printed copper nanowire electrode exhibits excellent activity and stability in the electrocatalytic reduction of nitrate to ammonia, achieving a Faradaic efficiency of 86.54% and an ammonia yield of 440.81 μmol / h / cm³. 2 .

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] 1. The 3D printing technology involved in this invention possesses rapid prototyping capabilities and design and printing flexibility, leading to significant advancements in materials manufacturing technology. Furthermore, 3D printing technology can easily print structures with complex geometries, tunable porosity, and dimensions, thereby alleviating multiple limitations associated with traditional manufacturing techniques. These 3D-printed catalyst structures, with their nanostructures at micron resolution, can induce pores and increase specific surface area, providing nanoscale features beneficial to catalytic reactions. Simultaneously, the designed structures can be modified using computer-aided design (CAD) software, offering simplicity, speed, and convenience.

[0032] 2. This invention utilizes steps such as 3D printing, chemical plating, chemical oxidation, and chemical reduction to control the morphology of 3D-printed copper electrodes, thereby synthesizing 3D-printed copper nanowire electrodes. These electrodes provide more active sites for the electrocatalytic NRA reaction and ensure sufficient contact with the electrolyte, facilitating mass transfer of reactants on the catalyst surface. The 3D-printed copper nanowire electrode exhibits excellent activity and stability in the electrocatalytic reduction of nitrate to ammonia, achieving a Faradaic efficiency of 86.54% and an ammonia yield of 440.81 μmol / h / cm³. 2 . Attached Figure Description

[0033] Figure 1 3D printed copper electrode E1 prepared in Comparative Example 3 ( Figure 1 (a) Comparative Example 4: 3D-printed copper hydroxide electrode E2 ( Figure 1 (b) and the 3D-printed copper nanowire electrode E3 prepared in Example 1. Figure 1 Image c) is a scanning electron microscope (SEM) image.

[0034] Figure 2 The images show the X-ray diffraction (XRD) patterns of sample E1 prepared in Comparative Example 3 and sample E3 prepared in Example 1.

[0035] Figure 3 This is the X-ray photoelectron spectroscopy (XPS) image of sample E3 prepared in Example 1. Figure 3 (a) and high-resolution Cu2p spectrum ( Figure 3 (b)

[0036] Figure 4 This is a linear sweep voltammetry (LSV) curve of the electrocatalytic nitrate-to-ammonia catalyst of Examples 1 and Comparative Examples 1-4, samples E1-E5.

[0037] Figure 5 The LSV curves of the 3D printed copper nanowire electrode E3 prepared in Example 1 in pure KOH and KOH + KNO3 solutions are shown.

[0038] Figure 6 The nitrate transammonia Faradaic efficiency of the 3D-printed copper nanowire electrode E3 prepared in Example 1 at different potentials during the NRA process is shown. Figure 6 a) and ammonia yield diagram ( Figure 6 (b)

[0039] Figure 7 The graph shows the nitrate conversion Faraday efficiency and ammonia yield of the 3D-printed copper nanowire electrode E3 prepared in Example 1 during the stability test.

[0040] Figure 8 This is the nuclear magnetic resonance (1H NMR) image obtained after the 3D printed copper nanowire electrode E3 prepared in Example 1 reacts in a 14 / 15N nitrate solution.

[0041] Figure 9 This is a process flow diagram of the present invention. Detailed Implementation

[0042] The following examples further illustrate the above-described content of the present invention, but it should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Example

[0043] Step S1: Design the electrode structure model using 3D modeling software. The electrode is an ordered porous array structure composed of 10×10 basic units, each basic unit being 0.1cm×0.1cm×0.1cm, with an overall size of 1cm×1cm×0.1cm and a porosity of 92%.

[0044] Step S2: Export the designed electrode model as an STL file, and then slice the STL file with a layer thickness of 10μm to obtain a series of two-dimensional images of the electrode structure.

[0045] Step S3: Import the 2D image of the sliced ​​electrode structure into the micro-nano 3D printer (Mop Precision's microArch® S240 (10μm precision), adjust the printing platform, set the printing parameters (10μm thickness per layer), start printing, remove the printed electrode, rinse with ethanol, and then cure in a UV curing oven for 2 minutes to obtain the 3D printed electrode A3.

[0046] Step S4: Take out the 3D printed electrode A3 and perform pretreatment for chemical plating. Immerse it in a mixed solution of KMnO4 (7.5 g / L) and KOH (20 g / L) (immersion temperature 40℃, immersion time 2 minutes), take it out and rinse it with deionized water, then immerse it in Na2S2O3 (5 g / L) solution (immersion temperature 60℃, immersion time 10 minutes), take it out and rinse it with deionized water and dry it (drying temperature 40℃, drying time 30 minutes). Finally, immerse it in a mixed solution of AgNO3 (2 g / L) and ethanol (50 ml / L) (immersion temperature 25℃, immersion time 10 minutes) to obtain the 3D printed electrode B3.

[0047] Step S4: Chemically plate the 3D-printed electrode B3 with copper in the following solutions: NaOH (10 g / L), CuSO4·5H2O (8 g / L), HCHO (12 ml / L), and C. 10 H 14 N2Na2O8 (2g / L), NaKC4H4O6 (2g / L), C 10 The copper electrode C3 was obtained by soaking in a solution of H8N2 (10 mg / L) and K4Fe(CN)6 (20 mg / L) (soaking temperature 45℃, soaking time 40 minutes) and then vacuum drying (drying temperature 60℃, drying time 6 hours).

[0048] Step S5: The 3D printed copper electrode C3 after chemical copper plating is oxidized by immersing it in 0.1M (NH4)2S2O8 and 1M NaOH solution (immersion time 1 hour) to obtain the 3D printed electrode D3 after chemical copper plating and oxidation treatment.

[0049] Step S6: The 3D printed electrode D3, after chemical copper plating and oxidation treatment, is subjected to heat reduction treatment in a tube furnace (heating temperature 300℃, heating time 1 hour, heating atmosphere hydrogen-argon mixture) to obtain the 3D printed copper nanowire electrode E3.

[0050] Comparative Example 1

[0051] Steps: Cut the copper sheet into a shape of 1cm×1cm×0.1cm to obtain sample (control sample) E4.

[0052] Comparative Example 2

[0053] Steps: Cut the copper foam into a shape of 1cm×1cm×0.1cm to obtain sample (control sample) E5.

[0054] Comparative Example 3

[0055] Step S1: Design the electrode structure model using 3D modeling software. The electrode is an ordered porous array structure composed of 10×10 basic units, each basic unit being 0.1cm×0.1cm×0.1cm, with an overall size of 1cm×1cm×0.1cm and a porosity of 92%.

[0056] Step S2: Export the designed electrode model as an STL file, and then slice the STL file with a layer thickness of 10μm to obtain a series of two-dimensional images of the electrode structure.

[0057] Step S3: Import the 2D image of the sliced ​​electrode structure into the micro-nano 3D printer (Mop Precision's microArch® S240 (10μm precision), adjust the printing platform, set the printing parameters (10μm thickness per layer), start printing, remove the printed electrode, rinse with ethanol, and then cure in a UV curing oven for 2 minutes to obtain the 3D printed electrode A1.

[0058] Step S4: Take out the 3D printed electrode A1 and perform a chemical plating pretreatment on it. Immerse it in a mixed solution of KMnO4 (7.5 g / L) and KOH (20 g / L) (immersion temperature 40℃, immersion time 2 minutes), take it out and rinse it with deionized water, then immerse it in a Na2S2O3 (5 g / L) solution (immersion temperature 60℃, immersion time 10 minutes), take it out and rinse it with deionized water and dry it (drying temperature 40℃, drying time 30 minutes). Finally, immerse it in a mixed solution of AgNO3 (2 g / L) and ethanol (50 mL / L) (immersion temperature 25℃, immersion time 10 minutes) to obtain the 3D printed electrode B1.

[0059] Step S5: Chemically plate the 3D-printed electrode B1 with copper in the following solutions: NaOH (10 g / L), CuSO4·5H2O (8 g / L), HCHO (12 mL / L), and C. 10 H 14 N2Na2O8 (2g / L), NaKC4H4O6 (2g / L), C 10The copper electrode E1 was obtained by soaking in a solution of H8N2 (10 mg / L) and K4Fe(CN)6 (20 mg / L) (soaking temperature 45℃, soaking time 40 minutes) and then vacuum drying (drying temperature 60℃, drying time 6 hours).

[0060] Comparative Example 4

[0061] Step S1: Design the electrode structure model using 3D modeling software. The electrode is an ordered porous array structure composed of 10×10 basic units, each basic unit being 0.1cm×0.1cm×0.1cm, with an overall size of 1cm×1cm×0.1cm and a porosity of 92%.

[0062] Step S2: Export the designed electrode model as an STL file, and then slice the STL file with a layer thickness of 10μm to obtain a series of two-dimensional images of the electrode structure.

[0063] Step S3: Import the 2D image of the sliced ​​electrode structure into the micro-nano 3D printer (Mop Precision's microArch® S240 (10μm precision), adjust the printing platform, set the printing parameters (10μm thickness per layer), start printing, remove the printed electrode, rinse with ethanol, and then cure in a UV curing oven for 2 minutes to obtain the 3D printed electrode A2.

[0064] Step S4: Take out the 3D printed electrode A2 and perform a chemical plating pretreatment on it. Immerse it in a mixed solution of KMnO4 (7.5 g / L) and KOH (20 g / L) (immersion temperature 40℃, immersion time 2 minutes), take it out and rinse it with deionized water, then immerse it in a Na2S2O3 (5 g / L) solution (immersion temperature 60℃, immersion time 10 minutes), take it out and rinse it with deionized water and dry it (drying temperature 40℃, drying time 30 minutes). Finally, immerse it in a mixed solution of AgNO3 (2 g / L) and ethanol (50 mL / L) (immersion temperature 25℃, immersion time 10 minutes) to obtain the 3D printed electrode B2.

[0065] Step S5: Chemically plate the 3D-printed electrode B2 with copper in the following solutions: NaOH (10 g / L), CuSO4·5H2O (8 g / L), HCHO (12 mL / L), and C. 10 H 14 N2Na2O8 (2g / L), NaKC4H4O6 (2g / L), C 10 The copper electrode C2 was obtained by soaking in a solution of H8N2 (10 mg / L) and K4Fe(CN)6 (20 mg / L) (soaking temperature 45℃, soaking time 40 minutes) and then vacuum drying (drying temperature 60℃, drying time 6 hours).

[0066] Step S6: The 3D printed copper electrode C2 after chemical copper plating is oxidized by immersing it in 0.1M (NH4)2S2O8 and 1M NaOH solution (immersion time 1 hour) to obtain the 3D printed electrode E2 after chemical copper plating and oxidation treatment.

[0067] NO3RR activity testing procedure: A series of prepared 3D printed electrodes (E1 / E2 / E3 / E4 / E5) were placed in a Pt sheet electrode holder as working electrodes, with mercury / mercuric oxide as the reference electrode and the Pt sheet as the counter electrode. 1 mol L... -1 KOH + 0.1 mol L -1 A KNO3 mixed aqueous solution was used as the electrolyte to construct a three-electrode testing system. LSV measurements were then performed to obtain the LSV polarization curves of catalysts E1–E5, with a scan rate of 10 mV / s. -1 The potential range is -0.4 to -1.6 V; in 1 mol L -1 KOH + 0.1 mol L -1 Chronocurrent response tests were conducted using a KNO3 mixed aqueous solution to obtain chronocurrent curves at different potentials for the E3 catalyst, with a reaction time of 1800 s. Indophenol blue assays were performed on the electrolytes under different catalysts using a UV-Vis spectrophotometer to obtain their UV-Vis spectrophotometric curves.

[0068] The surface morphology of samples E1, E2, and E3 was observed using SEM, such as... Figure 1 As shown in Figure ac, E1 clearly shows that its surface is granular ( Figure 1 In section a), after E2 undergoes surface oxidation, copper hydroxide nanoribbons are densely arranged on the surface. Figure 1 (b) After heating and reduction, the E3 surface becomes dense nanowires ( Figure 1 (c) Samples E1 and E3 were characterized by XRD, such as... Figure 2 As shown, diffraction peaks appeared, which perfectly matched the diffraction peaks of pure metallic Cu. Sample E3 was characterized by XPS, as shown... Figure 3 As shown, the Cu 2p spectrum of E3 ( Figure 3 In b), Cu can be fitted to two peaks, located at 932.8 eV and 952.7 eV respectively. 0 / 1+ No Cu 2+ The presence of Cu was not detected in the spectrum. + The weak satellite peaks indicate that Cu on the E3 surface is mainly in the form of Cu. 0 The form exists, which is consistent with the XRD results.

[0069] The NRA catalytic performance of the E1-E5 samples prepared in Example 1 and Comparative Examples 1-4 is as follows: Figure 4 As shown in the figure, the LSV curves of samples E1 to E5 show that sample E3 has the highest limiting reaction current, proving that sample E3 has the best NRA activity; Figure 6 As shown, the E3 sample exhibited the best performance in terms of ammonia yield and Faradaic efficiency at different potentials, with a Faradaic efficiency of 86.54% and an ammonia yield of 440.81 μmol / h / cm³. 2 ;like Figure 7 As shown, the ammonia yield and Faraday efficiency of E3 were calculated by UV colorimetric analysis of the electrolyte after 10 chronocurrent cycles at the optimal potential of -0.35V. No significant decrease was observed, indicating good durability. Figure 8 As shown, when using respectively 14N KNO3 and 15N KNO3 was used as the nitrogen source for the reaction. The resulting electrolyte was then subjected to nuclear magnetic resonance (NMR) analysis to obtain the 1H NMR spectrum. The results indicate that when the nitrogen source is... 14N When KNO3 is used, the ammonia product is... 14N NH3, when the nitrogen source is 15N When KNO3 is used, the ammonia product is... 15N The presence of NH3 clearly indicates that the ammonia product obtained after the reaction indeed originated from the KNO3 reactants.

[0070] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are only illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the scope of the principles of the present invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. A method for preparing a 3D-printed copper nanowire electrode for electrocatalytic reduction of nitrate to ammonia, characterized in that... The specific process is as follows: Step S1: Design the electrode structure model using 3D modeling software. The electrode is an ordered porous array structure composed of 10×10 basic units, each basic unit being 0.1cm×0.1cm×0.1cm, with an overall size of 1cm×1cm×0.1cm and a porosity of 92%. Step S2: Export the electrode structure model designed in Step S1 as an STL file, and then slice the STL file with a layer thickness of 10μm to obtain a series of two-dimensional images of the electrode structure. Step S3: Import the two-dimensional image of the electrode structure processed in step S2 into the micro-nano 3D printer, adjust the printing platform, set the printing parameters, start printing the electrode, take out the printed electrode, rinse it with ethanol, and then cure it in the UV curing oven for 2 minutes to obtain the 3D printed electrode. Step S4: The 3D printed electrode obtained in step S3 is subjected to chemical plating pretreatment by immersing it in a mixed solution of KMnO4 and KOH, rinsing it with deionized water, then immersing it in Na2S2O3 solution, rinsing it with deionized water and drying it, and finally immersing it in a mixed solution of AgNO3 and ethanol to obtain the chemically pretreated 3D printed electrode. Step S5: The 3D-printed electrode obtained from the pre-treatment in step S4 is subjected to electroless copper plating in an environment containing NaOH, CuSO4·5H2O, HCHO, and C. 10 H 14 N₂Na₂O₈, NaKC₄H₄O₆, C 10 The 3D-printed electrode was obtained by immersing in a solution of H8N2 and K4Fe(CN)6 and then vacuum drying. Step S6: The chemically plated copper 3D printed electrode obtained in step S5 is subjected to oxidation treatment by immersing it in a solution containing (NH4)2S2O8 and NaOH to obtain a chemically plated copper and oxidized 3D printed electrode. Step S7: The chemically plated and oxidized 3D printed electrode obtained in step S6 is subjected to a heat reduction treatment to obtain a 3D printed copper nanowire electrode.

2. The method for preparing the 3D-printed copper nanowire electrode for electrocatalytic reduction of nitrate to ammonia according to claim 1, characterized in that: The micro-nano 3D printer mentioned in step S3 is the microArch S240 from Mofang Precision. The optical precision of this micro-nano 3D printer is 10μm, and the printing layer thickness is 10-40μm.

3. The method for preparing the 3D-printed copper nanowire electrode for electrocatalytic reduction of nitrate to ammonia according to claim 1, characterized in that: In step S4, the pretreatment for electroless plating involves immersion in a solution of 7.5 g / L KMnO4 and 20 g / L KOH at 40°C for 2 minutes; immersion in a solution of 5 g / L Na2S2O3 at 60°C for 10 minutes; drying at 40°C for 30 minutes; and immersion in a solution of 2 g / L AgNO3 and 50 mL / L ethanol at 25°C for 10 minutes.

4. The method for preparing the 3D-printed copper nanowire electrode for electrocatalytic reduction of nitrate to ammonia according to claim 1, characterized in that: The conditions for electroless copper plating in step S5 are: NaOH 10 g / L, CuSO4·5H2O 8 g / L, HCHO 12 mL / L, C 10 H 14 N2Na2O8 2g / L, NaKC4H4O6 2g / L, C 10 The sample was soaked in a solution of 10 mg / L H8N2 and 20 mg / L K4Fe(CN)6 at 45°C for 40 minutes, and then vacuum dried at 60°C for 6 hours.

5. The method for preparing the 3D-printed copper nanowire electrode for electrocatalytic reduction of nitrate to ammonia according to claim 1, characterized in that: The oxidation treatment conditions in step S6 are: soaking in 0.1 mol / L (NH4)2S2O8 and 1 mol / L NaOH solution for 1 hour, followed by vacuum drying at 60°C for 6 hours.

6. The method for preparing a 3D-printed copper nanowire electrode for electrocatalytic reduction of nitrate to ammonia according to claim 1, characterized in that: The heating and reduction treatment in step S7 is performed under the following conditions: heating at 300°C for 1 hour in a tube furnace, with a hydrogen-argon mixture in the heating and reduction atmosphere.

7. The method for preparing a 3D-printed copper nanowire electrode for electrocatalytic reduction of nitrate to ammonia according to claim 1, characterized in that... The specific steps are as follows: Step S1: Design the electrode structure model using 3D modeling software. The electrode is an ordered porous array structure composed of 10×10 basic units, each basic unit being 0.1cm×0.1cm×0.1cm, with an overall size of 1cm×1cm×0.1cm and a porosity of 92%. Step S2: Export the electrode structure model designed in Step S1 as an STL file, and then slice the STL file with a layer thickness of 10μm to obtain a series of two-dimensional images of the electrode structure. Step S3: Import the two-dimensional image of the electrode structure processed in step S2 into the micro-nano 3D printer, adjust the printing platform, set the printing parameters, start printing the electrode, take out the printed electrode, rinse with ethanol, and then cure in the UV curing chamber for 2 minutes to obtain the 3D printed electrode. The micro-nano 3D printer is the microArch S240 of Mofang Precision. The optical precision of the micro-nano 3D printer is 10μm, and the printing layer thickness is 10μm. Step S4: The 3D printed electrode obtained in step S3 is immersed in a solution of KMnO4 7.5 g / L and KOH 20 g / L at 40°C for 2 minutes; immersed in a solution of Na2S2O3 5 g / L at 60°C for 10 minutes; dried at 40°C for 30 minutes; and immersed in a solution of AgNO3 2 g / L and ethanol 50 mL / L at 25°C for 10 minutes to obtain a 3D printed electrode pretreated with electroless plating. Step S5: The 3D printed electrode obtained from step S4 underwent pre-chemical plating treatment in a solution of NaOH 10 g / L, CuSO4·5H2O 8 g / L, HCHO 12 mL / L, and C 10 H 14 N2Na2O8 2g / L, NaKC4H4O6 2g / L, C 10 The electrode was immersed in a solution of 10 mg / L H8N2 and 20 mg / L K4Fe(CN)6 at 45°C for 40 minutes, and then dried at 60°C for 6 hours to obtain a chemically plated copper 3D printed electrode. Step S6: Immerse the chemically copper-plated 3D printed electrode obtained in step S5 in 0.1 mol / L (NH4)2S2O8 and 1 mol / L NaOH solution for 1 hour, and then vacuum dry at 60℃ for 6 hours to obtain a chemically copper-plated and oxidized 3D printed electrode. Step S7: Place the chemically plated and oxidized 3D printed electrode obtained in step S6 in a tube furnace and heat it at 300°C for 1 hour under a hydrogen-argon mixed gas to obtain a 3D printed copper nanowire electrode. This 3D-printed copper nanowire electrode provides more active sites for the electrocatalytic NRA reaction and allows for sufficient contact with the electrolyte, which is beneficial for mass transfer of reactants on the catalyst surface. The 3D-printed copper nanowire electrode exhibits excellent activity and stability in the electrocatalytic reduction of nitrate to ammonia, achieving a Faradaic efficiency of 86.54% and an ammonia yield of 440.81 μmol / h / cm³. 2 .

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