A dual-phase copper foam electrode for the electrocatalytic reduction of nitrate to ammonia in a membrane electrode assembly, and a preparation method and application thereof
By constructing a foamed copper electrode with an amorphous/crystalline biphase copper (a/c-Cu) structure, the problems of slow kinetics and poor stability of pure copper catalysts in the electrocatalytic reduction of nitrate were solved, and the high efficiency of electrocatalytic reduction of nitrate to ammonia was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2025-01-17
- Publication Date
- 2026-07-17
AI Technical Summary
Existing pure copper catalysts suffer from slow reaction kinetics and poor stability in the electrocatalytic reduction of nitrate, resulting in poor performance in practical applications.
A foamed copper electrode with an amorphous/crystalline dual-phase copper (a/c-Cu) structure is formed through calcination and electrochemical reduction to create a porous structure, thereby enhancing catalytic activity and stability.
It improves the activity and stability of nitrate electrocatalytic reduction to ammonia, with the highest ammonia Faraday efficiency reaching 92%, the highest current density reaching 3.5 A cm-2, and the highest energy efficiency reaching 26%. It can stably electrolyze for 300 hours at high current density.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of electrocatalytic reduction of nitrate to ammonia technology, and more particularly to a self-supporting biphase copper foam electrode and its application in membrane electrode systems for electrocatalytic reduction of nitrate to ammonia. The stable electrode structure design of the amorphous / crystalline biphase structure improves catalytic activity and reaction stability. Background Technology
[0002] Ammonia is an important raw material for agricultural and industrial chemicals, currently mainly produced through the Haber process under high temperature and high pressure conditions. This process accounts for approximately 1-2% of global energy consumption and is also one of the major sources of global carbon dioxide emissions. In the development of low-energy-consumption, low-carbon-emission green ammonia synthesis processes, electrocatalytic nitrate reduction based on renewable energy is a promising alternative route. By using nitrate pollutants as a nitrogen source and water as a hydrogen source, nitrate electrocatalytic reduction provides a low-carbon, sustainable ammonia synthesis pathway with broad application prospects.
[0003] Currently, copper, as a non-precious metal, is widely studied in the electrocatalytic reduction of nitrate due to its low cost and excellent adsorption capacity for nitrate ions. However, pure copper catalysts still suffer from slow reaction kinetics and poor stability in nitrate reduction. To address these issues, researchers have attempted to improve catalytic performance through various material design strategies, such as alloying and surface modification, but these methods have not yet been widely adopted in practical applications. Against this backdrop, this invention provides an electrocatalytic reduction process for ammonia production from nitrate based on a biphase copper foam electrode. By constructing a stable amorphous / crystalline biphase copper (a / c-Cu) structure, the catalytic activity and long-term stability of the foam copper electrode are significantly improved, providing a new technical approach for green ammonia synthesis. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing a biphase foamed copper electrode for the electrocatalytic reduction of nitrate to ammonia in a membrane electrode system. This method is simple, efficient, and yields a high ammonia production. The prepared foamed copper electrode exhibits high nitrate reduction activity and stability.
[0005] To achieve the above objectives, the technical solution of the present invention is as follows:
[0006] A method for preparing a biphase copper foam electrode for the electrocatalytic reduction of nitrate to ammonia in a membrane electrode system, comprising the following steps:
[0007] Step 1: Clean the foamed copper ultrasonically in ethanol, then dry it with argon gas, keeping the surface smooth; the foamed copper electrode area is 1-100 cm². 2 The thickness is 0.2-1.0 mm, and the porosity is 90-130 ppi.
[0008] Step 2: Place the prepared foamed copper electrode in a muffle furnace for calcination; the calcination time is 2.5-3.5 hours and the calcination temperature is 550-650℃.
[0009] Step 3: The calcined copper foam electrode is electrochemically reduced from copper oxide to metallic copper in an H-type electrolytic cell or membrane electrode electrolyzer, thereby forming an amorphous / crystalline biphase copper (a / c-Cu) electrode.
[0010] Based on the above scheme, preferably, the area of the copper foam can be 1-100 cm². 2 It has a thickness of 0.2 mm and a porosity of 110 ppi.
[0011] Based on the above scheme, preferably, the calcination temperature is 600℃ and the calcination time is 3h.
[0012] Based on the above scheme, preferably, the calcined foamed copper electrode is 1-100cm 2 In-situ reduction reaction was carried out in a large-scale MEA membrane electrode electrolyzer, with the cathode electrolyte being 1M KOH + 0.2M KNO3 or 0.5M KNO3, and an application of 0.1A cm⁻¹. -2 After the reduction current is applied until the membrane electrode electrolyzer voltage stabilizes, an amorphous / crystalline biphase copper (a / c-Cu) electrode is formed.
[0013] Based on the above scheme, preferably, the calcined foamed copper electrode is used in a 1cm... 2 In-situ reduction reaction is carried out in an H-type electrolytic cell at the working electrode. The cathode electrolyte is 1M KOH + 0.2M KNO3, and an application of 0.1A cm⁻¹ is applied. -2 After the reduction current is applied until the voltage of the H-type electrolytic cell stabilizes, an amorphous / crystalline dual-phase copper (a / c-Cu) electrode is formed.
[0014] The reactive electrolytic reduction device is a membrane electrode electrolytic cell.
[0015] The a / c-Cu electrode prepared by the method described above in this invention possesses a macroscopic porous structure. The electrode surface is composed of interconnected nano-copper particles; it has a microscopic porous structure; and it exhibits a dual-phase structure of crystalline and amorphous components, with TEM characterization determining that the amorphous component accounts for approximately 24%.
[0016] The a / c-Cu electrode prepared in this invention can be directly used in the electrocatalytic reduction of nitrate to ammonia reaction in a membrane electrode system. Specifically, this electrode exhibits a dual-phase structure of crystalline and amorphous components with a porous structure. When applied to the electrocatalytic reduction of nitrate, it demonstrates high electrolytic ammonia production performance. In MEA electrolyzer performance tests, the ammonia Faradaic efficiency reaches a maximum of 92%, and the ammonia current density reaches a maximum of 3.5 A cm⁻¹.-2 The full-cell energy efficiency reaches up to 26%, and it can operate at 1.5A cm⁻¹. -2 Stable electrolysis for 300 hours.
[0017] Performance testing of a self-supporting biphase copper foam electrode in a nitrate membrane electrode electrolyzer. The porous structure promotes nitrate mass transfer, and the biphase structure enhances reaction activity and stability.
[0018] The advantages of this invention over the prior art are:
[0019] This invention can easily and efficiently prepare materials up to 100 cm. 2 The electrode is directly used for the electrocatalytic reduction of nitrate. This a / c-Cu electrode exhibits a porous structure, effectively promoting the diffusion and migration of nitrate ions within the electrode. The electrode surface is rough and porous, possessing both crystalline and amorphous dual-phase structures. This results in excellent electrocatalytic reduction of nitrate to ammonia in MEA electrolyzers, achieving a maximum ammonia Faradaic efficiency of 92% and a maximum current density of 3.5 A / cm². -2 The full-cell energy efficiency reaches up to 26%, and it can operate at 1.5Acm. -2 The device was able to stably electrolyze at high current density for 300 hours. This invention provides an important research foundation for promoting the industrial application of ammonia production by electrocatalytic reduction of nitrate. Attached Figure Description
[0020] Figure 1 This is a physical image of the a / c-Cu electrode in Example 1.
[0021] Figure 2 These are scanning electron microscope images of the a / c-Cu electrode at different scales in Example 1.
[0022] Figure 3 This is a transmission electron microscope image of the a / c-Cu electrode in Example 1.
[0023] Figure 4 This is the X-ray diffraction pattern of the a / c-Cu electrode in Example 1.
[0024] Figure 5 The NO3 in the MEA electrolyzer of the a / c-Cu electrode in Example 1. - RR reaction performance diagram.
[0025] Figure 6 The NO3 in the MEA electrolyzer of the a / c-Cu electrode in Example 1. - RR stability test results.
[0026] Figure 7 It is 100cm in Example 2 2 a / c-Cu electrode in MEA electrolyzer NO3 -Photograph of the product after the RR reaction.
[0027] Figure 8 It is 100cm in Example 2 2 a / c-Cu electrode in MEA electrolyzer NO3 - RR reaction performance diagram.
[0028] Figure 9 The NO3 in the H-type electrolyzer of the a / c-Cu electrode in Example 3. - RR test results.
[0029] Figure 10 Comparative Example 1: NO3 in an MEA electrolyzer using a / c-Cu powder electrode - RR reaction performance diagram.
[0030] Figure 11 This is the X-ray diffraction pattern of the Cu foam electrode in Comparative Example 2.
[0031] Figure 12 Comparative Example 2: Cu foam electrode in MEA electrolyzer NO3 - RR reaction performance diagram.
[0032] Figure 13 This is the X-ray diffraction pattern of the a / c-Cu-H2 electrode in Comparative Example 3.
[0033] Figure 14 This is a transmission electron microscope image of the a / c-Cu-H2 electrode in Comparative Example 3.
[0034] Figure 15 Comparative Example 3: NO3 in MEA Electrolyte using a / c-Cu-H2 electrode - RR reaction performance diagram.
[0035] Figure 16 The X-ray diffraction patterns of the a / c-Cu-300 and a / c-Cu-900 electrodes in Comparative Example 4 are shown.
[0036] Figure 17 Comparative Example 4: NO3- in MEA electrolyzer using the a / c-Cu-300 electrode - RR reaction performance diagram.
[0037] Figure 18 Comparative Example 4: NO3- in MEA electrolyzer using the a / c-Cu-900 electrode - RR reaction performance diagram. Detailed Implementation
[0038] The entire process will now be described in detail with reference to the accompanying drawings and embodiments, but the claims of the present invention are not limited to these embodiments. Furthermore, the embodiments only provide some conditions for achieving this objective, and do not imply that these conditions must be met to achieve this objective. The scope of protection of the present invention should include the entire contents of the claims.
[0039] Example 1
[0040] Use copper foam electrodes (1 cm² in area) 2 The copper foam electrode (0.2 mm thick, 110 ppi porosity) was first ultrasonically cleaned in ethanol, then dried with argon gas while maintaining a smooth surface, and then calcined in a muffle furnace at 600 °C for 3 h. The calcined copper foam electrode was then used as the cathode working electrode in an MEA electrolytic cell for NO3 oxidation. - In-situ reduction under RR conditions. This MEA electrolyzer uses porous titanium foam coated with a commercial iridium black catalyst as the anode and counter electrode (4 cm² area). 2 A layer of N-methylpiperidine-terphenyl copolymer anion exchange membrane (approximately 24 μm thick) is sandwiched between the cathode working electrode and the anode counter electrode, thus forming a membrane electrode with a sandwich structure. Furthermore, both the cathode and anode plates are platinum-plated titanium plates with unidirectional serpentine flow fields, wherein the cathode serpentine flow field (area 1 cm²) 2 1M KOH + 0.2M KNO3 is introduced as the cathode electrolyte (flow rate 3 mL / min). -1 Anode serpentine flow field (area 4cm²) 2 1M KOH is introduced as the anolyte (flow rate 5 mL / min). -1 ). In NO3 - Apply 0.1 Acm during RR in situ reduction. -2 After the reduction current is applied until the MEA electrolyzer voltage stabilizes, an amorphous / crystalline dual-phase copper (a / c-Cu) electrode is formed during this process. Figure 1 This is a physical image of an a / c-Cu electrode. As can be seen from the image, the a / c-Cu electrode has a porous structure. Figure 2 The scanning electron microscope image (left) shows that the pore size of a / c-Cu is approximately 230 μm, which facilitates mass transfer and diffusion of the nitrate-containing electrolyte solution within the electrode. Figure 2 The scanning electron microscope image (right) shows that the surface of the a / c-Cu electrode is composed of many connected grains, exhibiting a microporous structure. Figure 3 These are transmission electron microscope (TEM) images of an a / c-Cu electrode, showing both crystalline and amorphous regions. Figure 4 The relatively weak and broad X-ray diffraction peaks indicate that the prepared a / c-Cu electrode has the characteristics of amorphous / crystalline dual-phase copper.
[0041] NO3 in MEA electrolyzer - RR performance testing was conducted using a constant current mode with an applied current density of 0.5-4 A / cm². -2 Electrolysis time was 15 minutes at each current density. The cathode outlet was connected to a three-necked flask for gas-liquid separation. The gaseous product was analyzed online for hydrogen content as a byproduct. The collected cathode and anode liquid products were analyzed quantitatively for ammonia and nitrite products using a UV spectrophotometer.
[0042] Figure 5 , 6 NO3 in an MEA electrolyzer with an a / c-Cu electrode - The RR performance test results show that the electrode has high activity and stability in the electrocatalytic reduction of nitrate to ammonia, with the highest ammonia Faradaic efficiency reaching 92% and the highest ammonia partial current density reaching 3.5 Acm. -2 The full-cell energy efficiency reaches up to 26%, and it can operate at 1.5A cm⁻¹. -2 Stable electrolysis for over 300 hours under high current density.
[0043] Example 2
[0044] The area of the copper foam in Example 1 was increased from 1 cm². 2 Increase to 100cm 2 After ultrasonic cleaning in ethanol, the surface is dried with argon gas, ensuring a smooth surface; then it is calcined in a muffle furnace at 600℃ for 3 hours, with a depth of 100cm. 2 In-situ electrochemical reduction in a MEA electrolytic cell. This MEA electrolytic cell uses porous titanium foam coated with a commercially available iridium black catalyst as the anode and counter electrode (100 cm² area). 2 A sandwich-structured membrane electrode is formed by sandwiching an N-methylpiperidine-terphenyl copolymer anion exchange membrane (approximately 24 μm thick) between the cathode working electrode and the anode counter electrode. Furthermore, both the cathode and anode plates are platinum-plated titanium plates with unidirectional serpentine flow fields, where the cathode serpentine flow field (area 100 cm²) is... 2 ) Introduce 1M KOH + 0.5M KNO3 as the cathode electrolyte (flow rate 50 mL / min) -1 ), Anode serpentine flow field (area 100cm²) 2 1 MkOH was introduced as the anolyte (flow rate 50 mL / min). -1 ). In NO3 - Apply 0.1 Acm during RR in situ reduction. -2 After the reduction current is applied until the MEA electrolyzer voltage stabilizes, 100 cm⁻¹ is formed during this process. 2 Amorphous / crystalline dual-phase copper (a / c-Cu) electrode. Figure 7 100cm 2The image shows a physical a / c-Cu electrode. As can be seen from the image, the electrode area has increased to 100 cm². 2 The electrode remains intact, and the electrode surface structure is uniform.
[0045] At 100cm 2 NO3 in MEA electrolyzer - RR performance testing employed a constant current mode, with an applied current ranging from 40-160A and an electrolysis time of 10 minutes at each current density. The cathode outlet was connected to a three-necked flask for gas-liquid separation. The gaseous product was analyzed online for hydrogen content as a byproduct. The collected cathode and anolyte liquid products were quantitatively analyzed using a UV spectrophotometer to determine ammonia and nitrite products. Figure 8 NO3 - The RR performance test results graph shows that at 100cm 2 The a / c-Cu electrode plate maintained high nitrate electrocatalytic activity. At a current of 160 A, the full-cell voltage was 2.23 V, the Faradaic efficiency for ammonia reached 94.6%, and the ammonia formation rate was 11.9 gh. -1 By increasing the area of the a / c-Cu electrode sheet to 100 cm² 2 The electrode still exhibits high performance in ammonia synthesis, indicating that the electrode preparation method of the present invention is easy to scale up industrially and holds promise for achieving industrial ammonia synthesis through simple and efficient electrode preparation.
[0046] Example 3
[0047] 1cm in Example 1 2 The foamed copper was ultrasonically cleaned in ethanol, dried with argon gas while maintaining a smooth surface, and then calcined in a muffle furnace at 600°C for 3 hours. It was then fixed 1 cm thick using platinum wire electrode clamps. 2 The calcined copper foam electrode was subjected to in-situ electrochemical reduction in an H-type electrolytic cell. This cell consisted of a cathode chamber, an anode chamber, and an anion exchange membrane. The cathode electrolyte was 1M KOH + 0.2M KNO3 (40 mL), and the anode electrolyte was 1M KOH (40 mL). The reduction was achieved by applying a 0.1 A cm⁻¹ electrode. -2 After the reduction current is applied until the voltage of the H-type electrolytic cell stabilizes, a 1cm layer is formed. 2 a / c-Cu electrode sheet. For example... Figure 9 As shown, at a cathode reduction potential of -2V vs. Ag / AgCl, the H-type electrolytic cell cannot continuously supply NO3. - The reactants cause their concentration to decrease with electrolysis time, gradually intensifying the hydrogen evolution side reaction and leading to a continuous decrease in cathode current. This is to ensure a continuous supply of NO3. -The reactants will be used to reduce the prepared a / c-Cu electrode in an H-type electrolytic cell, and then assembled into the membrane electrode electrolytic cell in Example 1 for NO3 reaction. - During the RR performance test, issues such as catalyst oxidation upon contact with air and electrode fragility make the actual operation difficult.
[0048] Comparative Example 1
[0049] The calcined copper foam electrode from Example 1 was ground into powder in a mortar, then mixed with Nafion resin and ultrasonically dispersed in ethanol. This mixture was then coated onto the surface of a carbon felt to prepare a conventional powder electrode, wherein the catalyst loading was 10 mg / cm³. -2 In the MEA electrolytic cell of Example 1, this a / c-Cu powder electrode was used as the working electrode, replacing the a / c-Cu foam self-supporting electrode in Example 1, to complete the NO3 production process. - RR performance testing. (By...) Figure 10 As can be seen, at the same current density as in Example 1, using a conventional a / c-Cu powder electrode sheet significantly increases the hydrogen evolution side reaction and the full cell voltage, resulting in a decrease in the yield of ammonia products and a decrease in the energy efficiency of the full cell.
[0050] Comparative Example 2
[0051] The foamed copper from Example 1 was first ultrasonically cleaned in ethanol, then dried with argon gas while maintaining a smooth surface. Without undergoing muffle furnace calcination, it was considered to lack amorphous characteristics and possess a fully crystalline copper structure. It was then directly used as the working electrode in the MEA electrolytic cell of Example 1, replacing the a / c-Cu foam self-supporting electrode of Example 1, to complete the NO3... - RR performance test. Figure 11 The figure shows the X-ray diffraction pattern of the Cu foam electrode. As can be seen, compared to the a / c-Cu electrode in Example 1, the untreated Cu foam electrode exhibits higher XRD peak intensity and sharper peak shape, indicating stronger crystallinity and a lower proportion of amorphous structure. Under the same performance testing conditions as in Example 1, it was applied to the electrocatalytic reduction reaction of nitrate. Figure 12 Performance test results show that the Cu foam electrode sheet exhibits poor electrolysis performance, with the highest ammonia Faraday efficiency at 81% and the highest ammonia partial current density at only 2.49 A cm⁻¹. -2 ,pass Figure 12 Compared with Example 1 Figure 4 The comparison shows that the Cu foam electrode exhibits significantly lower reactivity compared to the a / c-Cu electrode treated with prior oxidation followed by electrochemical reduction, at 4 A cm⁻¹. -2 Under current density conditions, the voltage needs to be 0.4V higher, which leads to a decrease in the energy efficiency of the entire battery.
[0052] Comparative Example 3
[0053] The foamed copper electrode calcined at 600℃ in Example 1 was placed in a tube furnace and heat-treated at 350℃ for 3 hours under argon gas containing 5% H2 to obtain an a / c-Cu-H2 electrode. Figure 13 The figure shows the X-ray diffraction pattern of the a / c-Cu-H2 electrode. As can be seen from the figure, compared to the a / c-Cu electrode formed by electrochemical in-situ reduction in Example 1, the a / c-Cu-H2 electrode prepared by hydrogen thermal reduction exhibits stronger crystallinity. Figure 14 Transmission electron microscopy images of a / c-Cu-H2 show that the amorphous region accounts for only 5.5%, which is significantly lower than that of the a / c-Cu electrode in Example 1.
[0054] Under the same performance testing conditions as in Example 1, it was applied to the electrocatalytic reduction reaction of nitrate. Figure 15 Performance test results show that the a / c-Cu-H2 electrode exhibits poor electrolysis performance, with the highest ammonia Faraday efficiency at 81% and the highest partial current density of ammonia at only 2.5 Acm. -2 ,pass Figure 15 Compared with Example 1 Figure 4 The comparison shows that the a / c-Cu-H2 electrode treated with hydrogen reduction exhibits significantly lower reactivity than the a / c-Cu electrode treated with electrochemical in-situ reduction, at 4 Acm. -2 Under current density conditions, the voltage needs to be 0.36V higher, which leads to a decrease in the overall energy efficiency of the battery.
[0055] Comparative Example 4
[0056] The foamed copper electrode sheet from Example 1 was first ultrasonically cleaned in ethanol, then dried with argon gas while maintaining a smooth surface. It was then calcined in a muffle furnace at 300°C and 900°C for 3 hours each. The calcined foamed copper electrode was used as the cathode working electrode in the MEA electrolytic cell of Example 1 for NO3 oxidation. - In-situ reduction under RR conditions. Apply 0.1 Acm. -2 After the reduction current is applied until the voltage of the membrane electrode electrolyzer stabilizes, a / c-Cu-300 and a / c-Cu-900 electrode sheets are formed.
[0057] Figure 16The figures show the X-ray diffraction patterns of a / c-Cu-300, a / c-Cu, and a / c-Cu-900 electrodes. As can be seen, different precursor heat treatment temperatures during muffle furnace calcination can alter the crystallinity of the electrodes after electrochemical reduction. Higher calcination temperatures lead to a gradual decrease in the crystallinity of the electrodes after electrochemical in-situ reduction. Under the same performance testing conditions as in Example 1, these electrodes were applied to the electrocatalytic reduction of nitrate. Figure 17 and 18 The figures show the performance test results of a / c-Cu-300 and a / c-Cu-900 electrodes in the same MEA electrolyzer as in Example 1, respectively. It can be seen that differences in electrode crystallinity also lead to differences in performance. Specifically, in... Figure 17 NO3 in the a / c-Cu-300 electrode - The RR exhibited the worst performance and the highest rate of hydrogen evolution side reaction, while Example 1... Figure 5 a / c-Cu electrode and Figure 18 The a / c-Cu-900 electrode exhibits similar product selectivity at various current densities, but the a / c-Cu-900 electrode requires a voltage 0.2V higher, leading to a decrease in energy efficiency.
[0058] Comparative Example 5
[0059] The foamed copper electrode calcined at 600℃ in Example 1 was placed in a tube furnace and heated in 100 mL / min. -1 Under a methane atmosphere, thermal reduction at 600°C for 3 hours yielded an a / c-Cu-CH4 electrode. The electrode after methane heat treatment turned reddish-brown, indicating complete reduction to elemental copper in the reducing atmosphere of methane. It was then assembled into the MEA membrane electrode electrolyzer of Example 1 for nitrate electrocatalytic reduction at 0.5 A / cm². -2 Hydrogen byproducts already appear at current densities low, and the hydrogen evolution side reaction intensifies as the reaction proceeds. This may be because during the thermal reduction of methane, some carbon deposits form on the electrode surface, occupying the active sites of the catalyst and hindering the proton-electron transfer process at the electrode interface, thereby inhibiting the electrocatalytic reduction of nitrate to ammonia.
[0060] Comparative Example 6
[0061] The foamed copper electrode calcined at 600℃ in Example 1 was directly used in the MEA electrolytic cell of Example 1 to process NO3. - RR in-situ reduction (cathode electrolyte is 1M KOH + 0.2M KNO3), wherein the 0.1Acm was not passed. -2 The reduction current treatment involves directly applying 0.5Acm. -2The electrocatalytic reduction of nitrate is carried out using a large instantaneous current. Due to this instantaneously applied large current, a portion of the CuO precursor is instantly converted into elemental copper, which then undergoes the electrocatalytic reduction of nitrate. The electrochemical reduction of the remaining CuO precursor competes with the electrocatalytic reduction of nitrate, resulting in incomplete and uneven reduction of the CuO precursor. Compared to Example 1, this incomplete electrochemical reduction significantly reduces the number of active sites in the electrode structure, thereby decreasing the activity of the electrocatalytic reduction of nitrate to ammonia.
[0062] It should be noted that, according to the above embodiments of the present invention, those skilled in the art can fully realize the scope of the independent claims and dependent claims of the present invention, and the implementation process and method are the same as those in the above embodiments; and the parts of the present invention not described in detail belong to the well-known technology in the art.
[0063] The above description is only a part of the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a biphase copper foam electrode for the electrocatalytic reduction of nitrate to ammonia in a membrane electrode system, characterized in that, Includes the following steps: Step 1: Clean the foamed copper ultrasonically in ethanol, then dry it with argon gas, keeping its surface smooth; the foamed copper electrode area is 1-100 cm². 2 The thickness is 0.2-1.0 mm, and the porosity is 90-130 ppi. Step 2: Place the prepared foamed copper electrode in a muffle furnace for calcination; the calcination time is 2.5-3.5 hours and the calcination temperature is 550-650℃. Step 3: The calcined foamed copper electrode is electrochemically reduced from copper oxide to metallic copper in an H-type electrolytic cell or membrane electrode electrolyzer, thereby forming an amorphous / crystalline dual-phase copper (a / c-Cu) electrode.
2. The preparation method according to claim 1, characterized in that: In step 1, the area of the copper foam is 1-100 cm². 2 The thickness is 0.2-1.0 mm, and the porosity is 90-130 ppi.
3. The preparation method according to claim 1, characterized in that: The area of the copper foam is 1-100 cm² 2 It has a thickness of 0.2 mm and a porosity of 110 ppi.
4. The preparation method according to claim 1, characterized in that: The calcination temperature is 600℃ and the calcination time is 3 hours.
5. The preparation method according to claim 1, characterized in that: The calcined copper foam electrode underwent an in-situ reduction reaction in a MEA membrane electrode electrolyzer. The cathode electrolyte was either 1M KOH + 0.2M KNO3 or 0.5M KNO3, and a 0.1A cm⁻¹ pressure was applied. -2 After the reduction current is applied until the membrane electrode electrolyzer voltage stabilizes, an amorphous / crystalline biphase copper (a / c-Cu) electrode is formed.
6. The preparation method according to claim 1, characterized in that: The calcined copper foam electrode underwent an in-situ reduction reaction in an H-type electrolytic cell. The cathode electrolyte was 1M KOH + 0.2M KNO3, and an A cm⁻¹ pressure was applied. -2 After the reduction current is applied until the voltage of the H-type electrolytic cell stabilizes, an amorphous / crystalline dual-phase copper (a / c-Cu) electrode is formed.
7. A self-supporting biphase copper foam electrode, characterized in that: The self-supporting biphase copper electrode is prepared by the preparation method as described in any one of claims 1 to 6.
8. The application of the self-supporting biphase copper foam electrode as described in claim 7 in the electrocatalytic reduction of nitrate to ammonia in a membrane electrode system.