Electrolysis device for preparing ammonia by alkaline electrolysis of nitrate

Abstract

The utility model relates to the technical field of electro-catalysis ammonia production, in particular to an electrolysis device for ammonia production by alkaline electrolysis of nitrate, which comprises a plurality of electrolysis units and end plates positioned at two ends, the plurality of electrolysis units are overlapped between the two groups of end plates, an anode plate is arranged between the left end plate and the electrolysis unit, and a cathode plate is arranged between the right end plate and the electrolysis unit. A cathode plate is arranged between the right side end plate and the electrolysis unit, and electrode terminals are fixedly arranged on the upper sides of the anode plate and the cathode plate; the electrolysis unit is composed of two sets of bipolar electrode plates, two sets of partition plates and electrolysis cavity grooves, the two sets of partition plates are arranged between the two sets of bipolar electrode plates, the electrolysis cavity grooves are formed in the two sets of partition plates, a diaphragm is arranged between the two sets of partition plates, an anode catalyst layer is arranged on the left side of the diaphragm, and a cathode catalyst layer is arranged on the right side of the diaphragm. According to the utility model, the copper / oxygen double-defect Cu2O-coated Cu heterojunction catalytic electrode is adopted, so that the catalytic activity and selectivity are improved, the energy consumption and the cost are reduced, and a new technical path is provided for green low-carbon ammonia synthesis.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of electrocatalysis ammonia production, and particularly relates to an electrolytic device for alkaline electrolysis of nitrate to produce ammonia. BACKGROUND

[0002] Currently, ammonia is mainly produced by the Haber-Bosch process in industry, which requires high temperature (400-500°C) and high pressure (150-300 atm) conditions, high energy consumption, and a large amount of carbon dioxide emissions. Existing nitrate wastewater treatment technologies mainly rely on biological or chemical methods. The biological method is slow and sensitive to environmental variables; the chemical method has high cost, low selectivity, and low yield.

[0003] In recent years, electrocatalytic reduction of nitrate has gradually attracted attention due to its green and efficient characteristics. This technology reduces nitrate to ammonia through the catalytic action of electrode materials, with green and efficient characteristics. However, existing electrode materials have problems such as insufficient active sites, low electron transfer efficiency, and easy deactivation, which limit their practical application.

[0004] Currently, the main electrode materials include noble metals (such as Pt, Pd) and non-noble metals (such as Cu, Ni, Fe), but noble metal catalysts are high in cost and difficult to apply on a large scale, while non-noble metal catalysts have low activity and selectivity, which easily leads to the generation of by-products (such as N2O, NO2-) and reduces ammonia yield. Moreover, most non-noble metal electrodes will form an oxidation layer on the surface or lose catalyst after long-term operation, resulting in a decrease in electrolysis efficiency. In addition, some catalysts are easily corroded in alkaline electrolytes, affecting the service life.

[0005] Therefore, it is of great significance to develop an efficient, stable, and low-cost electrolytic device for promoting the industrial application of electrochemical ammonia synthesis technology. SUMMARY

[0006] In view of the existing deficiencies, the purpose of the utility model is to provide an electrolytic device for alkaline electrolysis of nitrate to produce ammonia, which uses a copper / oxygen double-defect Cu2O@Cu heterojunction catalytic electrode to improve catalytic activity and selectivity and reduce energy consumption and cost.

[0007] To achieve the above purpose, the technical scheme adopted by the utility model is as follows:

[0008] An electrolysis device for producing ammonia from nitrates by alkaline electrolysis includes multiple electrolysis units and end plates at both ends. The multiple electrolysis units are stacked between two sets of end plates. An anode plate is provided between the left end plate and the electrolysis unit, and a cathode plate is provided between the right end plate and the electrolysis unit. Electrode terminals are fixed on the upper side of both the anode plate and the cathode plate. The two sets of end plates are connected by multiple sets of long screws. The long screws are fixedly connected to the end plates by fastening nuts. The electrolysis units are located between the multiple sets of long screws.

[0009] The electrolysis unit consists of two sets of bipolar electrode plates, two sets of partitions, and an electrolysis chamber. Two sets of partitions are provided between the two sets of bipolar electrode plates. An electrolysis chamber is opened inside each of the two sets of partitions. A membrane is provided between the two sets of partitions. An anode catalyst layer is provided on the left side of the membrane, and a cathode catalyst layer is provided on the right side of the membrane.

[0010] Furthermore, the bipolar electrode plate is composed of electrode layer A, insulating membrane, nickel hydroxide layer, nickel plate layer, nickel hydroxyl oxide layer and electrode layer B. The nickel plate layer is the base layer, with nickel hydroxide layer on its left side and nickel hydroxyl oxide layer on its right side. Electrode layer A is located outside the nickel hydroxide layer, and electrode layer B is located outside the nickel hydroxyl oxide layer. Insulating membranes are provided between the nickel hydroxide layer and electrode layer A, and between the nickel hydroxyl oxide layer and electrode layer B.

[0011] Furthermore, the cathode catalyst layer is a copper / oxygen dual-defect site Cu2O@Cu heterojunction catalytic electrode, and both electrode layer A and electrode layer B are copper foam electrodes with a copper / oxygen dual-defect site Cu2O@Cu heterojunction structure.

[0012] Furthermore, the left end plate is provided with an electrolyte inlet for injecting electrolyte, and the right end plate is provided with an electrolyte outlet at the same position as the electrolyte inlet. A gas outlet is provided above the electrolyte outlet. A gas flow hole and an electrolyte flow hole are provided on the bipolar electrode plate. The gas flow hole is connected to the gas outlet. The electrolyte flow hole is connected to both the electrolyte inlet and the electrolyte outlet. Both the gas flow hole and the electrolyte flow hole are connected to the electrolysis chamber.

[0013] Furthermore, the end plate is made of stainless steel, and the partition is made of nickel-plated steel.

[0014] Furthermore, the electrode terminals on the anode plate are connected to the positive terminal of the power supply, and the electrode terminals on the cathode plate are connected to the negative terminal of the power supply.

[0015] Optionally, the thickness of the anode catalyst layer is 10-200 μm; the thickness of the cathode catalyst layer is 1-200 μm.

[0016] Preferably, the thickness of the anode catalyst layer is 20-100 μm; the thickness of the cathode catalyst layer is 5-100 μm.

[0017] Optionally, the catalyst in the cathode catalyst layer is selected from one or more of Fe, Co, Ni, Mo or their alloys or composite catalysts, and the catalyst in the anode catalyst layer is selected from one or more of RanyNi, NiCo2O4, LaNiO3 and Ni-Co-P alloys.

[0018] Optionally, the membrane is selected from one or more of polyphenylene sulfide (PPS) membranes, polyetheretherketone (PEEK) fiber membranes, and polysulfone fiber membranes.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. This invention employs a copper / oxygen dual-defect Cu2O@Cu heterojunction catalytic electrode, which improves catalytic activity and selectivity while reducing energy consumption and cost. It provides a new technical route for green and low-carbon ammonia synthesis. The Cu2O@Cu heterojunction electrode successfully overcomes the problems existing in traditional electrode materials, provides a new solution for low-cost non-precious metal catalysts, and breaks through the technical barriers of traditional wet denitrification and electrocatalytic ammonia production. This technology can be widely used in fields such as flue gas denitrification in thermal power plants, industrial wastewater treatment, and green ammonia synthesis, and has significant environmental and economic benefits.

[0021] 2. This utility model isolates the gas through a partition, and sets nickel hydroxide layer and nickel hydroxyl oxide layer on both sides of the bipolar electrode plate respectively. The positive and negative electrodes of the power supply are switched through the two electrode ends, so as to realize the simultaneous production of ammonia and oxygen in one device system. The gas phase oxygen is discharged and collected from the gas outlet, and the liquid phase ammonia solution flows out from the electrolyte outlet to achieve product separation. Attached Figure Description

[0022] Fig. 1 This is a schematic diagram of the overall structure of this utility model.

[0023] Fig. 2 This is a schematic diagram of the structure of this utility model from another angle.

[0024] Fig. 3 This is a cross-sectional view of the present invention.

[0025] Fig. 4 This is a schematic diagram of the disassembled structure of this utility model.

[0026] Fig. 5 This is a schematic diagram of the disassembled structure of the electrolysis unit in this utility model.

[0027] Fig. 6This is a schematic diagram of the cross-sectional structure of the bipolar plate in this utility model.

[0028] In the diagram: 1. Long screw; 2. Fastening nut; 3. End plate; 4. Electrolyte inlet; 5. Electrode terminal; 6. Electrolysis unit; 61. Bipolar electrode plate; 611. Electrode layer A; 612. Insulating diaphragm; 613. Nickel hydroxide layer; 614. Nickel plate layer; 615. Nickel oxide layer; 616. Electrode layer B; 62. Separator; 63. Electrolysis chamber; 64. Anode catalyst layer; 65. Diaphragm; 66. Cathode catalyst layer; 67. Gas flow hole; 68. Electrolyte flow hole; 7. Gas outlet; 8. Electrolyte outlet; 9. Anode plate; 10. Cathode plate. Detailed Implementation

[0029] The technical solutions of this utility model will be clearly and completely described below with reference to the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0030] Example: Figs. 1 to 6 As shown, an electrolysis device for producing ammonia from nitrates by alkaline electrolysis includes multiple electrolysis units 6 and end plates 3 located at both ends. The multiple electrolysis units 6 are stacked between two sets of end plates 3. An anode plate 9 is provided between the left end plate 3 and the electrolysis unit 6, and a cathode plate 10 is provided between the right end plate 3 and the electrolysis unit 6. Electrode terminals 5 are fixed on the upper side of both the anode plate 9 and the cathode plate 10 for connecting to a power source to form an electrolysis circuit. The two sets of end plates 3 are connected by multiple sets of long screws 1. The long screws 1 are fixedly connected to the end plates 3 by fastening nuts 2. The electrolysis units 6 are located between the multiple sets of long screws 1.

[0031] The electrolysis unit 6 consists of two sets of bipolar electrode plates 61, two sets of partitions 62, and an electrolysis chamber 63. Two sets of partitions 62 are provided between the two sets of bipolar electrode plates 61. Each set of partitions 62 has an electrolysis chamber 63 inside to contain the electrolyte. A diaphragm 65 is provided between the two sets of partitions 62. The diaphragm 65 divides the electrolysis chamber 63 into an anode side and a cathode side. An anode catalyst layer 64 is provided on the left side of the diaphragm 65, and a cathode catalyst layer 66 is provided on the right side of the diaphragm 65.

[0032] In this embodiment, the bipolar electrode plate 61 is composed of an electrode layer A611, an insulating membrane 612, a nickel hydroxide layer 613, a nickel plate layer 614, a nickel hydroxyl oxide layer 615, and an electrode layer B616. The nickel plate layer 614 serves as the base layer, with the nickel hydroxide layer 613 on its left side and the nickel hydroxyl oxide layer 615 on its right side. The electrode layer A611 is located outside the nickel hydroxide layer 613, and the electrode layer B616 is located outside the nickel hydroxyl oxide layer 615. Insulating membranes 612 are provided between the nickel hydroxide layer 613 and the electrode layer A611, and between the nickel hydroxyl oxide layer 615 and the electrode layer B616. This multi-layer structure design gives the bipolar electrode plate 61 higher activity and selectivity. Nickel hydroxide and nickel hydroxyl oxide, as active materials, provide abundant active sites, which is beneficial for the electrolysis reaction. The nickel plate layer 614, as the base layer, provides good mechanical strength and conductivity, ensuring the stability and durability of the electrode. The insulating diaphragm 612 effectively prevents short circuits and improves the safety of the electrolysis device.

[0033] In this embodiment, the cathode catalyst layer 66 is a copper / oxygen dual-defect site Cu2O@Cu heterojunction catalytic electrode, and electrode layers A611 and B616 are both copper / oxygen dual-defect site Cu2O@Cu heterojunction foamed copper electrodes. The Cu2O@Cu heterojunction structure combines the advantages of both Cu2O and Cu materials. Cu2O, as a p-type semiconductor, exhibits good catalytic activity, while Cu provides good conductivity. The dual-defect site design further increases the number of active sites on the catalyst, which is beneficial for the electrolysis reaction. The foamed copper electrode has a three-dimensional porous structure, providing a larger specific surface area, which facilitates sufficient contact between the electrolyte and the electrode, thereby improving electrolysis efficiency. The combination of the Cu2O@Cu heterojunction structure and foamed copper ensures the catalytic activity of the electrode while improving its mechanical strength and stability. The copper / oxygen dual-defect site Cu2O@Cu heterojunction structure possesses unique catalytic properties, which can improve the rate and selectivity of the electrolysis reaction.

[0034] In this embodiment, the left end plate 3 is provided with an electrolyte inlet 4 for injecting electrolyte, and the right end plate 3 is provided with an electrolyte outlet 8 at the same position as the electrolyte inlet 4 for discharging the used electrolyte. A gas outlet 7 is provided on the upper side of the electrolyte outlet 8 for discharging the gas generated during the electrolysis process. The bipolar electrode plate 61 is provided with a gas flow hole 67 and an electrolyte flow hole 68. The gas flow hole 67 is connected to the gas outlet 7, and the electrolyte flow hole 68 is connected to the electrolyte inlet 4 and the electrolyte outlet 8. Both the gas flow hole 67 and the electrolyte flow hole 68 are connected to the electrolysis chamber 63.

[0035] In this embodiment, end plate 3 is made of stainless steel. Stainless steel has good corrosion resistance, which can resist corrosive substances in the electrolyte and extend the service life of the electrolysis device. Stainless steel also has high mechanical strength, which can withstand the pressure and vibration generated during electrolysis and ensure the stability of the device. Partition 62 is made of nickel-plated steel. Nickel-plated steel has a layer of nickel plated on its surface, which improves its conductivity and facilitates electron transfer during electrolysis. The nickel layer also has good corrosion resistance, which can protect the steel from electrolyte corrosion and extend the service life of partition 62.

[0036] In this embodiment, the electrode terminal 5 on the anode plate 9 is connected to the positive terminal of the power supply, and the electrode terminal 5 on the cathode plate 10 is connected to the negative terminal of the power supply. The anode plate 9 serves as the positive electrode in the electrolysis reaction, and its electrode terminal 5 is connected to the positive terminal of the power supply to ensure that the anode plate 9 can receive positive charges and undergo an oxidation reaction. The cathode plate 10 serves as the negative electrode in the electrolysis reaction, and its electrode terminal 5 is connected to the negative terminal of the power supply to ensure that the cathode plate 10 can receive negative charges and undergo a reduction reaction.

[0037] Optionally, the thickness of the anode catalyst layer 64 is 10-200 μm; the thickness of the cathode catalyst layer 66 is 1-200 μm.

[0038] Preferably, the thickness of the anode catalyst layer 64 is 20-100 μm; the thickness of the cathode catalyst layer 66 is 5-100 μm.

[0039] Optionally, the catalyst in the cathode catalyst layer 66 is selected from one or more of Fe, Co, Ni, Mo or their alloys or composite catalysts, and the catalyst in the anode catalyst layer 64 is selected from one or more of RanyNi, NiCo2O4, LaNiO3 and Ni-Co-P alloys.

[0040] Optionally, the diaphragm 65 is selected from one or more of polyphenylene sulfide (PPS) diaphragm 65, polyetheretherketone (PEEK) fiber diaphragm 65, and polysulfone fiber diaphragm 65.

[0041] It should be noted that the copper / oxygen dual-defect site Cu2O@Cu heterojunction catalytic electrode is obtained by in-situ reconstruction of Cu2O particles and electrode surface in a copper acetate / acetic acid system using a specially treated copper foam substrate through electrodeposition. The resulting electrode is the OVs-Cu2O@DCF heterojunction catalytic electrode.

[0042] Optionally, copper foam (CF, 130 ppi) is cut into 10 mm × 10 mm slices and cleaned sequentially with acetone, hydrochloric acid, and anhydrous alcohol to remove organic impurities from the surface of the copper foam. Then, the copper foam with surface impurities removed is ultrasonically treated in deionized water (DI) for 30 minutes. Finally, it is vacuum dried at 60°C for 12 hours, ultimately forming copper defects (DCF) caused by ultrasonic cavitation. 0.3194 g of copper acetate monohydrate and 0.6562 g of sodium acetate are dissolved in 80 ml of... Electrodeposition electrolyte was prepared in ultrapure water, with the pH adjusted to 5.7 using acetic acid. Electrodeposition cathode preparation: In a three-electrode system, using different substrates (CF / DCF) as working electrodes, a Pt sheet as the counter electrode, and Ag / AgCl as the reference electrode, a constant voltage (-0.2, -0.4, and -0.6 V vs Ag / AgCl) was applied to different substrates at different times (20, 40, and 60 minutes) using a chronoamperometry method to obtain OVs-Cu₂O precatalyst. The electrodeposition product was vacuum dried at 60 °C for 12 h before being used for the electrocatalytic reduction of nitrates.

[0043] Optionally, in the initial stage of electrocatalytic reduction of nitrate, OVs-Cu2O will be further reconstructed during the electrochemical reduction process to form Cu@Cu2O heterojunction, thereby preparing different OVs-Cu2O@DCF or OVs-Cu2O@CF electrodes.

[0044] The working principle of an electrolysis device for producing ammonia from alkaline nitrates:

[0045] The electrolyte is injected into the electrolysis device through the electrolyte inlet 4 on the left end plate 3. The electrolyte circulates within the electrolysis unit 6, enters the electrolysis chamber 63 through the electrolyte flow hole 68, and is discharged through the electrolyte outlet 8 after the electrolysis reaction. The electrode terminal 5 on the anode plate 9 is connected to the positive terminal of the power supply, making the anode plate 9 positively charged and initiating an oxidation reaction. Under the action of the anode catalyst layer 64, hydroxide ions (OH-) in the electrolyte lose electrons, generating oxygen and water. The electrode terminal 5 on the cathode plate 10 is connected to the negative terminal of the power supply, making the cathode plate 10 negatively charged and initiating a reduction reaction. Under the action of the copper / oxygen double-defect site Cu2O@Cu heterojunction catalytic electrode in the cathode catalyst layer 66, nitrate ions (NO3-) in the electrolyte gain electrons and combine with hydrogen ions (H+) to generate ammonia and water. The gases generated during electrolysis, mainly ammonia and oxygen, are collected through the gas flow hole 67 to the gas outlet 7 and discharged from the electrolysis device. The used electrolyte is discharged through electrolyte outlet 8 for subsequent processing or recycling.

[0046] The bipolar electrode plate 61 consists of a multi-layer structure, including electrode layer A611, insulating membrane 612, nickel hydroxide layer 613, nickel plate layer 614, nickel hydroxyl oxide layer 615, and electrode layer B616. This structure provides abundant active sites, which is beneficial to the electrolysis reaction and improves the activity and selectivity of the electrode. Nickel hydroxide and nickel hydroxyl oxide, as active materials, participate in the electrolysis reaction, promoting electron transfer and ion exchange. Nickel plate layer 614, as the base layer, provides good mechanical strength and conductivity, ensuring the stability and durability of the electrode. The insulating membrane 612 effectively prevents short circuits and improves the safety of the electrolysis device. The cathode catalyst layer 66, a copper / oxygen dual-defect site Cu2O@Cu heterojunction catalytic electrode, combines the advantages of both Cu2O and Cu materials, exhibiting good catalytic activity and conductivity, further improving the rate and selectivity of the electrolysis reaction.

[0047] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating this utility model, and are not intended to limit the implementation of this utility model. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. Any obvious variations or modifications derived from the technical solutions of this utility model are still within the protection scope of this utility model.

Claims

1. An electrolytic device for producing ammonia from nitrates using alkaline electrolysis, characterized in that: It includes multiple electrolysis units (6) and end plates (3) located at both ends. The multiple electrolysis units (6) are stacked between two sets of end plates (3). An anode plate (9) is provided between the left end plate (3) and the electrolysis unit (6), and a cathode plate (10) is provided between the right end plate (3) and the electrolysis unit (6). Electrode terminals (5) are fixed on the upper side of both the anode plate (9) and the cathode plate (10). The two sets of end plates (3) are connected by multiple sets of long screws (1). The long screws (1) are fixedly connected to the end plates (3) by fastening nuts (2). The electrolysis unit (6) is located between the multiple sets of long screws (1). The electrolysis unit (6) consists of two sets of bipolar electrode plates (61), two sets of partitions (62), and an electrolysis chamber (63). Two sets of partitions (62) are provided between the two sets of bipolar electrode plates (61), and an electrolysis chamber (63) is provided inside each of the two sets of partitions (62). A membrane (65) is provided between the two sets of partitions (62). An anode catalyst layer (64) is provided on the left side of the membrane (65), and a cathode catalyst layer (66) is provided on the right side of the membrane (65).

2. The electrolytic apparatus for producing ammonia from alkaline nitrates according to claim 1, characterized in that: The bipolar electrode plate (61) is composed of electrode layer A (611), insulating membrane (612), nickel hydroxide layer (613), nickel plate layer (614), nickel hydroxyl oxide layer (615) and electrode layer B (616). The nickel plate layer (614) is the base layer, with nickel hydroxide layer (613) on its left side and nickel hydroxyl oxide layer (615) on its right side. Electrode layer A (611) is located outside the nickel hydroxide layer (613), and electrode layer B (616) is located outside the nickel hydroxyl oxide layer (615). Insulating membrane (612) is provided between the nickel hydroxide layer (613) and electrode layer A (611) and between the nickel hydroxyl oxide layer (615) and electrode layer B (616).

3. The electrolytic apparatus for producing ammonia from alkaline nitrates according to claim 2, characterized in that: The cathode catalyst layer (66) is a copper / oxygen double defect site Cu2O@Cu heterojunction catalytic electrode, and the electrode layer A (611) and electrode layer B (616) are both copper foam electrodes with copper / oxygen double defect site Cu2O@Cu heterojunction structure.

4. The electrolytic apparatus for producing ammonia from alkaline nitrates according to claim 1, characterized in that: The left end plate (3) is provided with an electrolyte inlet (4) for injecting electrolyte, and the right end plate (3) is provided with an electrolyte outlet (8) at the same position as the electrolyte inlet (4). The electrolyte outlet (8) is provided with a gas outlet (7) on its upper side. The bipolar electrode plate (61) is provided with a gas flow hole (67) and an electrolyte flow hole (68). The gas flow hole (67) is connected to the gas outlet (7). The electrolyte flow hole (68) is connected to the electrolyte inlet (4) and the electrolyte outlet (8). The gas flow hole (67) and the electrolyte flow hole (68) are both connected to the electrolysis chamber (63).

5. The electrolytic apparatus for producing ammonia from alkaline nitrates according to claim 1, characterized in that: The end plate (3) is a stainless steel plate, and the partition plate (62) is a nickel-plated steel plate.

6. The electrolytic apparatus for producing ammonia from alkaline nitrates according to claim 1, characterized in that: The electrode terminals (5) on the anode plate (9) are connected to the positive terminal of the power supply, and the electrode terminals (5) on the cathode plate (10) are connected to the negative terminal of the power supply.

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