Electrode and device for electrochemically synthesizing ammonia and electrode for nitrogen removal treatment of waste water and / or waste gas

Abstract

The invention provides an electrode and device for electrochemically synthesizing ammonia and an electrode for wastewater and / or waste gas denitrification treatment, and belongs to the technical field of electrocatalytic materials and the technical field of ammonia synthesis. The electrode for electrochemically synthesizing ammonia comprises a conductive substrate and a two-dimensional conjugated metal phthalocyanine polymer loaded on the conductive substrate, wherein the structure of the two-dimensional conjugated metal phthalocyanine polymer comprises a metal-nitrogen coordination center as shown in a formula (I); formula (I); wherein M1, M2, M3 and M4 are respectively and independently selected from any one of nickel, iron, copper, cobalt, zinc and manganese.

Description

Technical Field

[0001] This application relates to the fields of electrocatalytic materials technology and ammonia synthesis technology, and particularly to an electrode and apparatus for electrochemical ammonia synthesis, as well as an electrode for wastewater and / or waste gas denitrification treatment. Background Technology

[0002] Ammonia (NH3), as an important chemical raw material and potential energy carrier, is traditionally synthesized using the energy-intensive and emission-prone Haber-Bosch process. Electrochemical ammonia synthesis offers a new approach to achieving green ammonia synthesis at ambient temperature and pressure, while also enabling the co-treatment of nitrogen-containing wastewater and waste gas.

[0003] However, in practical applications, electrocatalysts for electrocatalytic ammonia synthesis face the following key technical bottlenecks, especially the severe performance degradation of non-precious metal catalysts under a wide range of operating conditions. These bottlenecks limit their large-scale industrial application.

[0004] (1) Narrow potential window: Most catalysts only exhibit high Faraday efficiency (FE) within a narrow potential range. Once the potential deviates from the optimal value, the FE drops sharply, resulting in a significant reduction in system efficiency under fluctuating power supply conditions driven by actual renewable energy sources (such as solar and wind power).

[0005] (2) Poor adaptability to nitrate or nitrite concentration: The catalyst has a weak adaptability to the range of actual wastewater concentration. The concentration of nitrate or nitrite in actual wastewater varies widely (from tens of ppm to thousands of ppm). Existing catalysts often only maintain high performance at specific concentrations. At low concentrations, the activity decreases significantly, and at high concentrations, the selectivity may be reduced due to mass transfer limitations or increased side reactions.

[0006] (3) The trade-off between activity and selectivity: FE decreases significantly at high current densities. Increasing the current density often comes at the cost of FE, especially at high overpotentials, where competition for hydrogen evolution reaction (HER) intensifies, leading to a decrease in ammonia selectivity.

[0007] (4) Insufficient long-term stability: Many catalysts deactivate their active sites, collapse their structures, or dissolve metals after long-term operation, resulting in performance degradation.

[0008] (5) Dependence on precious metals and cost issues: Although precious metal-based catalysts such as platinum and ruthenium have performed well, their high cost and scarcity have restricted their large-scale application. Summary of the Invention

[0009] In view of this, this application provides an electrode, apparatus, and electrode for the electrochemical synthesis of ammonia, as well as an electrode for the denitrification treatment of wastewater and / or exhaust gas. This application designs a high-performance two-dimensional conjugated metal phthalocyanine polymer catalyst at the molecular level and loads it onto a conductive substrate to form an electrode. Through synergistic effects of structural regulation, electronic structure optimization, and interface engineering, it achieves electrochemical ammonia synthesis with wide potential, wide concentration, high efficiency, and high stability.

[0010] According to one aspect of the present application, an electrode for electrochemical synthesis of ammonia is provided, characterized in that the electrode for electrochemical synthesis of ammonia comprises a conductive substrate and a two-dimensional conjugated metal phthalocyanine polymer loaded on the conductive substrate, wherein the structure of the two-dimensional conjugated metal phthalocyanine polymer contains a metal-nitrogen coordination center as shown in formula (I).

[0011] Equation (I);

[0012] Among them, M1, M2, M3 and M4 are each independently selected from any one of nickel, iron, copper, cobalt, zinc and manganese.

[0013] In another aspect of this application, an apparatus for electrochemically synthesizing ammonia is provided. The apparatus includes: the electrodes described above for electrochemically synthesizing ammonia; an electrolytic cell; and an electrolyte located in the electrolytic cell, wherein the electrolyte contains a nitrogen source.

[0014] In another aspect of this application, an electrode for denitrification treatment of wastewater and / or exhaust gas is provided. The electrode includes a conductive substrate and a two-dimensional conjugated metal phthalocyanine polymer loaded on the conductive substrate. The structure of the two-dimensional conjugated metal phthalocyanine polymer includes a metal-nitrogen coordination center as shown in formula (I).

[0015] Equation (I);

[0016] Among them, M1, M2, M3 and M4 are each independently selected from any one of nickel, iron, copper, cobalt, zinc and manganese.

[0017] The two-dimensional conjugated metal phthalocyanine polymer provided in this application possesses well-defined M-N4 active centers, high specific surface area, hydrophobic surface, and good charge transport capability, exhibiting good catalytic activity. Loading the two-dimensional conjugated metal phthalocyanine polymer onto a conductive substrate allows it to serve as a highly efficient electrocatalytic electrode for the electrochemical synthesis of ammonia. It maintains high Faradaic efficiency (>80%, up to 99.7%) and high ammonia yield (up to 32.8 gh) over a wide potential range (0.0 V to -1.5 V vs. reversible hydrogen electrode (RHE)) and a wide nitrogen salt concentration range (1.0 mmol / L to 5.0 mol / L). -1 g cat-1 It exhibits excellent catalytic activity and selectivity, and also has excellent long-term stability. Attached Figure Description

[0018] The above and other objects, features, and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0019] Figure 1 A schematic diagram of the synthetic route for the two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) in Example 1 of this application is shown;

[0020] Figure 2 The SEM image of the nickel phthalocyanine monomer (NiPc) in Comparative Example 1 of this application is shown;

[0021] Figure 3 The SEM image of the nickel phthalocyanine polymer (NiPcP) in Example 1 of this application is shown;

[0022] Figure 4 A TEM image of the nickel phthalocyanine polymer (NiPcP) in Example 1 of this application is shown;

[0023] Figure 5 The diagram shows a performance comparison of the electrodes provided in Example 1 (NiPcP) and Comparative Example 1 (NiPc) for electrochemical ammonia synthesis at different voltages for electrocatalytic reduction of nitrate to ammonia.

[0024] Figure 6 The diagram shows a comparison of the electrocatalytic ammonia synthesis performance of electrodes provided in Example 1 (NiPcP) and Comparative Example 1 (NiPc) of this application at different nitrate concentrations.

[0025] Figure 7 The It curve of the electrode for electrochemical ammonia synthesis provided in Example 1 of this application is shown in a 48-hour stability test;

[0026] Figure 8 The XRD comparison diagrams of the nickel phthalocyanine monomer (NiPc) in Comparative Example 1 and the two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) in Example 1 are shown.

[0027] Figure 9 Electrochemical impedance spectra of nickel phthalocyanine monomer (NiPc) in Comparative Example 1 and nickel phthalocyanine polymer (NiPcP) in Example 1 are shown.

[0028] Figure 10 A comparison diagram of Ni 2p values ​​is shown between the nickel phthalocyanine monomer (NiPc) in Comparative Example 1 and the nickel phthalocyanine polymer (NiPcP) in Example 1 of this application.

[0029] Figure 11 A comparison diagram of the contact angles of the nickel phthalocyanine monomer (NiPc) in Comparative Example 1 and the nickel phthalocyanine polymer (NiPcP) in Example 1 of this application is shown. Detailed Implementation

[0030] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0032] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). When using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0033] Metal phthalocyanine materials have attracted attention due to their well-defined metal-nitrogen four-coordinate structure (M-N4 structure), tunable electronic properties, and low cost. However, their monomeric form has poor conductivity and low utilization of active sites, which limits their electrocatalytic performance.

[0034] In realizing the concept of this application, it was discovered that two-dimensional conjugated polymers can enhance conductivity, expose more active sites, and optimize intermediate adsorption behavior through structural design, which is an effective strategy to improve electrocatalytic performance.

[0035] Specifically, according to an embodiment of the first aspect of this application, an electrode for electrochemical synthesis of ammonia is provided, characterized in that the electrode for electrochemical synthesis of ammonia comprises a conductive substrate and a two-dimensional conjugated metal phthalocyanine polymer loaded on the conductive substrate, wherein the structure of the two-dimensional conjugated metal phthalocyanine polymer contains a metal-nitrogen coordination center as shown in formula (I).

[0036] Equation (I);

[0037] M1, M2, M3, and M4 are each independently selected from any one of nickel, iron, copper, cobalt, zinc, and manganese. Preferably, M1, M2, M3, and M4 are each independently selected from one or two of nickel, iron, copper, cobalt, zinc, and manganese.

[0038] It is understood that in this application, M1, M2, M3 and M4 may be the same or different.

[0039] The two-dimensional conjugated metal phthalocyanine polymers provided in this application possess well-defined M-N4 active centers, high specific surface area, hydrophobic surfaces, and good charge transport capabilities, exhibiting excellent catalytic activity. Loading these polymers onto a conductive substrate allows them to serve as highly efficient electrocatalytic electrodes for the electrochemical synthesis of ammonia. They maintain high Faradaic efficiency (>80%, up to 99.7%) and high ammonia yield (up to 32.8 gh) over a wide potential range (0.0 V to -1.5 V vs. RHE) and a wide nitrogen salt concentration range (1.0 mmol / L to 5.0 mol / L). -1 g cat -1 It exhibits excellent catalytic activity and selectivity, and also has excellent long-term stability.

[0040] The electrode for electrochemical ammonia synthesis provided in this application has good prospects for industrial application and can be widely used in electrochemical ammonia synthesis systems, especially suitable for intermittent operating conditions driven by renewable energy.

[0041] This application not only provides a high-performance electrochemical ammonia synthesis catalyst, but more importantly, it provides a universal design strategy for synergistically regulating the structure, electronic state, and interface properties of the catalyst by constructing a two-dimensional conjugated metal-organic framework.

[0042] Furthermore, the electrode for electrochemical ammonia synthesis provided in this application does not require the addition of substances such as carbon black, effectively avoiding the hydrogen evolution competition reaction. In some embodiments of this application, the conductive substrate may include at least one of carbon cloth, carbon paper, nickel foam, nickel mesh, iron mesh, and stainless steel mesh. Preferably, the conductive substrate may be carbon cloth.

[0043] In some embodiments of this application, the loading amount of the two-dimensional conjugated metal phthalocyanine polymer on the conductive substrate can be 0.1 mg / cm². 2 ~ 5.0 mg / cm 2 For example, the loading amount of the two-dimensional conjugated metal phthalocyanine polymer on the conductive substrate can be 0.1 mg / cm³. 2 0.5 mg / cm 2 1.0 mg / cm 2 2.0 mg / cm 2 3.0 mg / cm 2 4.0 mg / cm 2 5.0 mg / cm 2 Or the range between any two of the above values.

[0044] In some embodiments of this application, the two-dimensional conjugated metal phthalocyanine polymer may have a mesoporous structure. In this application, the mesoporous structure may refer to a porous structure in which the pore size is between 2 nm and 50 nm.

[0045] In some embodiments of this application, the two-dimensional conjugated metal phthalocyanine polymer can be prepared by thermal shrinkage polymerization of a transition metal salt with 1,2,4,5-tetracyanobenzene. Specifically, the two-dimensional conjugated metal phthalocyanine polymer is prepared by the following method: a mixture of a transition metal salt and 1,2,4,5-tetracyanobenzene is heat-treated in a vacuum or inert atmosphere, and then washed and dried to obtain the two-dimensional conjugated metal phthalocyanine polymer.

[0046] This application describes the preparation of two-dimensional conjugated metal phthalocyanine polymers using transition metal salts and 1,2,4,5-tetracyanobenzene as raw materials via high-temperature thermal polycondensation under vacuum or inert gas conditions. The resulting two-dimensional conjugated metal phthalocyanine polymers possess a layered porous structure, high-density M-N4 active centers, good electrical conductivity, and a hydrophobic surface.

[0047] The two-dimensional conjugated metal phthalocyanine polymer preparation process provided in this application is simple, low-cost, and environmentally friendly: the raw materials are readily available, the synthesis method is a one-step thermal polycondensation, which does not require complex templates or post-processing, and it does not contain precious metals. It is suitable for the treatment of nitrogen-containing wastewater and waste gas and green ammonia synthesis, and meets the requirements of green chemistry and industrial production.

[0048] In some embodiments of this application, the transition metal salt may include at least one of anhydrous nickel salt, anhydrous iron salt, anhydrous ferrous salt, anhydrous copper salt, anhydrous cobalt salt, anhydrous zinc salt, and anhydrous manganese salt. The nickel salt may include at least one of anhydrous nickel chloride, anhydrous nickel nitrate, anhydrous nickel acetate, and anhydrous nickel sulfate. The iron salt may include at least one of anhydrous ferric chloride, anhydrous ferric nitrate, anhydrous ferric acetate, and anhydrous ferric sulfate. The ferrous salt may include at least one of anhydrous ferrous chloride, anhydrous ferrous nitrate, anhydrous ferrous acetate, and anhydrous ferrous sulfate. The copper salt may include at least one of anhydrous copper chloride, anhydrous copper nitrate, anhydrous copper acetate, and anhydrous copper sulfate. The cobalt salt may include at least one of anhydrous cobalt chloride, anhydrous cobalt nitrate, anhydrous cobalt acetate, and anhydrous cobalt sulfate. The zinc salt may include at least one of anhydrous zinc chloride, anhydrous zinc nitrate, anhydrous zinc acetate, and anhydrous zinc sulfate. The manganese salt may include at least one of anhydrous manganese chloride, anhydrous manganese nitrate, anhydrous manganese acetate, and anhydrous manganese sulfate.

[0049] The molar ratio of the transition metal salt to 1,2,4,5-tetracyanobenzene can be (1:1) to (1:3), preferably 1:2. For example, the molar ratio of the transition metal salt to 1,2,4,5-tetracyanobenzene can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, or any two of the above ratios.

[0050] The mixture of transition metal salt and 1,2,4,5-tetracyanobenzene can be obtained by mixing the transition metal salt and 1,2,4,5-tetracyanobenzene and then grinding them. The grinding time can be 20 min to 120 min, preferably 40 min. Exemplarily, the grinding time is within the range of any two of 20 min, 40 min, 60 min, 80 min, 100 min, 120 min, or more. The grinding can be manual or machine-based; this application does not have a particular limitation, as long as the purpose of this application is achieved.

[0051] In this application, an inert atmosphere can refer to a gaseous environment that is chemically inert and will not react chemically with reactants or products. For example, an inert atmosphere may include at least one of nitrogen, argon, and helium. The vacuum or inert atmosphere in this application is preferably a vacuum condition.

[0052] The heat treatment temperature can be between 200°C and 600°C. For example, the heat treatment temperature can be any two values ​​between 200°C, 300°C, 400°C, 500°C, 600°C, and above, preferably 400°C. The heat treatment time can be between 2 hours and 6 hours. For example, the heat treatment time can be any two values ​​between 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, and above, preferably 4 hours.

[0053] In this application, the product can be washed sequentially with an organic solvent and deionized water. Optionally, it can be washed three times each with ethanol and deionized water, and then placed in a vacuum oven to dry for 12 hours. After vacuum drying, a two-dimensional conjugated metal phthalocyanine polymer can be obtained.

[0054] An embodiment of the second aspect of this application provides an apparatus for electrochemically synthesizing ammonia, the apparatus comprising: the aforementioned electrode for electrochemically synthesizing ammonia; an electrolytic cell; and an electrolyte located in the electrolytic cell, the electrolyte containing a nitrogen source.

[0055] In some embodiments of this application, the electrolytic cell is an H-type electrolytic cell or a flowing electrolytic cell.

[0056] The pH of the electrolyte can be from 1 to 14. For example, the pH of the electrolyte can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or any two of the above values. Preferably, the electrolyte may contain 1 mol / L of KOH, with a pH of 14.

[0057] The operating potential of the apparatus for electrochemical ammonia synthesis can be 0.0 to -1.5 V (vs. RHE). For example, the operating potential of the apparatus for electrochemical ammonia synthesis can be 0.0, -0.2 V, -0.5 V, -0.8 V, -1.0 V, -1.2 V, -1.5 V, or any two of the above values.

[0058] The nitrogen source may include at least one of nitrate, nitrite, nitrogen dioxide, nitric oxide, nitrous oxide, and nitrogen gas. The electrolyte containing the nitrogen source may be a solution containing nitrate and / or nitrite; or a nitrogen-containing gas, such as nitrogen dioxide, nitric oxide, nitrous oxide, or nitrogen gas, may be introduced into the solution. The nitrogen-containing substance is reduced to ammonia through an electrocatalytic reduction reaction in the nitrogen-containing electrolyte.

[0059] When the nitrogen source includes nitrate and / or nitrite, the concentration of nitrate and / or nitrite can be from 1.0 mmol / L to 5.0 mol / L. For example, the concentration of nitrate and / or nitrite can be within the range of 1.0 mmol / L, 2.0 mmol / L, 3.0 mmol / L, 4.0 mmol / L, 5.0 mmol / L, or any two of these values.

[0060] Optionally, a three-electrode system can be used. In an electrolytic cell, the electrode used for electrochemical synthesis of ammonia described above is used as the working electrode, a silver / silver chloride electrode or a mercury / mercury oxide electrode is used as the reference electrode, and a platinum sheet or carbon rod is used as the counter electrode. An electrocatalytic reduction reaction is carried out in an electrolyte containing a nitrogen source to reduce the nitrogen-containing substance (nitrogen source) to ammonia, thereby performing an electrochemical synthesis of ammonia.

[0061] An embodiment of the third aspect of this application provides an application of an electrochemical ammonia synthesis apparatus in the field of electrochemical ammonia synthesis. The apparatus for electrochemical ammonia synthesis provided in this application has good industrial application prospects and can be widely used in electrochemical ammonia synthesis systems, especially suitable for intermittent operation driven by renewable energy sources.

[0062] An embodiment of the fourth aspect of this application provides an electrode for denitrification treatment of wastewater and / or exhaust gas, the electrode comprising a conductive substrate and a two-dimensional conjugated metal phthalocyanine polymer loaded on the conductive substrate, the two-dimensional conjugated metal phthalocyanine polymer containing a metal-nitrogen coordination center as shown in formula (I);

[0063] Equation (I);

[0064] Among them, M1, M2, M3 and M4 are each independently selected from any one of nickel, iron, copper, cobalt, zinc and manganese.

[0065] The electrode for denitrification of wastewater and / or exhaust gas described in this application can achieve efficient denitrification and resource recovery of nitrate-polluted water bodies such as industrial wastewater and agricultural runoff.

[0066] The preparation methods for the conductive substrate, the two-dimensional conjugated metal phthalocyanine polymer, and the electrode are described above and will not be repeated here. The preparation method of the two-dimensional conjugated metal phthalocyanine polymer provided in this application is simple, low-cost, and does not require precious metals. It is suitable for the resource-based treatment of green ammonia synthesis and nitrogen-containing wastewater or nitrogen-containing waste gas, and has significant environmental and energy application value.

[0067] An embodiment of the fifth aspect of this application provides an apparatus for denitrification treatment of wastewater and / or exhaust gas, the apparatus comprising: the aforementioned denitrification treatment for wastewater and / or exhaust gas.

[0068] An embodiment of the sixth aspect of this application provides an apparatus for denitrification treatment of wastewater and / or exhaust gas, and provides the application of the apparatus for denitrification treatment of wastewater and / or exhaust gas in the denitrification treatment of wastewater and / or exhaust gas.

[0069] The present application will now be described in detail with reference to embodiments to facilitate understanding by those skilled in the art. It is important to note that the embodiments are merely illustrative and should not be construed as limiting the scope of protection of the present application. Non-essential improvements and adjustments made to the present application by those skilled in the art based on the above description should still fall within the scope of protection of the present application. Furthermore, any raw materials not described in detail below are commercially available products; any process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art. All raw materials described in this application are obtained commercially, and all materials used in this application are commonly used in the art.

[0070] Example 1

[0071] This embodiment provides an electrode for the electrochemical synthesis of ammonia.

[0072] The electrode includes a conductive substrate and a two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) loaded on the conductive substrate. The structure of the two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) contains a metal-nitrogen coordination center as shown in formula (Ⅰ) above, wherein M1, M2, M3 and M4 are all nickel.

[0073] The preparation method of the electrode used for electrochemical ammonia synthesis is as follows:

[0074] (1) Synthesis of two-dimensional conjugated nickel phthalocyanine polymer (NiPcP)

[0075] Figure 1 A schematic diagram of the synthetic route for the two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) in Example 1 of this application is shown. Figure 1 As shown, 1 mmol of anhydrous NiCl2 and 2 mmol of 1,2,4,5-tetracyanobenzene were weighed and placed in a mortar, and thoroughly ground and mixed for 40 min until a uniform powder was obtained. The mixture was transferred to a quartz boat, placed in a tube furnace, and evacuated to a pressure <10 Pa. The temperature was increased to 400℃ at 5℃ / min for heat treatment, and held at that temperature for 4 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The solid product was removed and washed three times each with anhydrous ethanol and deionized water, and dried in a vacuum oven at 60℃ for 12 h to obtain black NiPcP powder, i.e., two-dimensional conjugated nickel phthalocyanine polymer (NiPcP).

[0076] (2) Preparation of electrodes for electrochemical ammonia synthesis

[0077] Take 3 mg of NiPcP powder obtained in step (1), add 0.5 mL of deionized water, 0.45 mL of isopropanol and 50 μL of Nafion solution (5wt%), and ultrasonically disperse for 30 min to form a uniform catalyst slurry. Use a micropipette to take 0.1 mL of the slurry and uniformly drop it onto the surface of a pretreated 1 cm × 1 cm carbon cloth. After air drying at room temperature, place it in a vacuum oven at 60℃ for 2 h to dry, obtaining a catalyst loading of 0.3 mg / cm. 2 The working electrode.

[0078] Comparative Example 1

[0079] This comparative example provides an electrode for electrochemical ammonia synthesis and its preparation method. Referring to Example 1, the difference is that in this comparative example, the electrode for electrochemical ammonia synthesis includes a conductive substrate and a nickel phthalocyanine monomer (NiPc) loaded on the conductive substrate. In the preparation method of the electrode for electrochemical ammonia synthesis, the nickel phthalocyanine monomer (NiPc) is purchased directly; in step (2), the NiPcP powder is replaced with an equal mass of commercial nickel phthalocyanine monomer (NiPc).

[0080] Figure 2 The SEM image of the nickel phthalocyanine monomer (NiPc) in Comparative Example 1 of this application is shown; Figure 3 The SEM image of the nickel phthalocyanine polymer (NiPcP) in Example 1 of this application is shown; Figure 4 A TEM image of the nickel phthalocyanine polymer (NiPcP) from Example 1 of this application is shown. Figures 2-4 It can be seen that a single nickel phthalocyanine (NiPc) monomer molecule is a disordered fragmented particle, while polyniphthalocyanine (NiPcP) can be seen to exhibit a smooth two-dimensional sheet-like morphology with regular wrinkles after pyrolysis at 400℃.

[0081] The electrocatalytic ammonia synthesis performance was tested using the electrodes provided in Example 1 and Comparative Example 1, respectively. The specific methods and test results are as follows:

[0082] An H-type electrolytic cell was used, with the electrodes prepared in Example 1 and Comparative Example 1 for electrochemical ammonia synthesis as the working electrodes, Hg / HgO as the reference electrode, and a carbon rod as the counter electrode. The electrolyte was 0.1 mol / L Na₂HPO₄ + 1.0 mol / L KNO₃ (pH = 9.2). Argon gas was purged for 30 min before electrolysis to remove dissolved oxygen. Electrolysis was performed at constant potential for 2 h at -0.5 V, -0.6 V, -0.7 V, -0.8 V, -0.9 V, and -1.0 V (vs. RHE) on a CHI760E electrochemical workstation.

[0083] Figure 5The diagram shows a performance comparison of the electrodes provided in Example 1 (NiPcP) and Comparative Example 1 (NiPc) for electrochemical ammonia synthesis at different voltages. Figure 5 It can be seen that the electrode provided in Example 1 of this application for electrochemical ammonia synthesis exhibits excellent wide potential adaptability, with the FE of the two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) exceeding 80% in the range of -0.5 V to -0.9 V. In Example 1, after electrolysis, a certain amount of electrolyte was taken, and the NH4+ was determined using the indophenol blue method. + Based on the concentration, the calculated FE at -0.7 V is 99.7%, and the highest ammonia yield is 5.9 gh at -1.0 V. -1 g cat -1 In contrast, the nickel phthalocyanine monomer (NiPc) electrode provided in Example 1, at -0.8 V vs. RH, showed a maximum FE of only 47.2%, while the highest ammonia yield was only 1.07 gh. -1 g cat -1 Furthermore, the performance significantly decreases at low applied potentials, indicating that the polymer structure of this application significantly improves the electrochemical ammonia synthesis performance of nickel phthalocyanine.

[0084] In the aforementioned 0.1 mol / L Na2HPO4 background electrolyte, KNO3 solutions of 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1.0 mol / L, and 2.0 mol / L were prepared using two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) and commercial nickel phthalocyanine monomer (NiPc) working electrodes, respectively, and the wide nitrate concentration adaptability test was conducted at -0.7 V (vs. RHE).

[0085] Figure 6 The diagram shows a performance comparison of the electrodes for electrochemical ammonia synthesis provided in Example 1 (NiPcP) and Comparative Example 1 (NiPc) of this application at different nitrate concentrations. Figure 6 As can be seen, the electrode for electrochemical ammonia synthesis provided in Example 1 of this application has an FE greater than 95% in the range of 0.05 mol / L to 2.0 mol / L, and the highest ammonia yield at 2.0 mol / L is 14.2 gh. -1 g cat -1 Even at 0.01 mol / L, the FE is still higher than 80%, indicating that the two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) has an extremely wide tolerance to nitrate concentrations. The polymer structure of this application significantly improves the electrochemical ammonia synthesis performance of nickel phthalocyanine.

[0086] The electrode provided in Example 1 for electrochemical ammonia synthesis was used to conduct stability tests on electrocatalytic ammonia synthesis. The specific methods and test results are as follows:

[0087] An H-type electrolytic cell was used, with the electrode prepared in Example 1 for electrochemical ammonia synthesis as the working electrode, Hg / HgO as the reference electrode, and a carbon rod as the counter electrode. The electrolyte was 0.1 mol / L Na2HPO4 + 2.0 mol / L KNO3 (pH = 9.2), and continuous electrolysis was performed at a constant potential of -0.7 V (vs. RHE) for 48 h.

[0088] Figure 7 The It curve of the electrode for electrochemical ammonia synthesis provided in Example 1 of this application is shown in a 48-hour stability test. Figure 7 It can be seen that the current density and ammonia yield do not decrease significantly, indicating that the two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) has excellent long-term electrochemical stability.

[0089] Example 2

[0090] This embodiment provides an electrode for the electrochemical synthesis of ammonia.

[0091] The electrode includes a conductive substrate and a two-dimensional conjugated copper phthalocyanine polymer (CuPcP) loaded on the conductive substrate. The structure of the two-dimensional conjugated copper phthalocyanine polymer (CuPcP) contains a metal-nitrogen coordination center as shown in formula (Ⅰ) above, wherein M1, M2, M3 and M4 are all copper.

[0092] In this embodiment, the preparation method of the two-dimensional conjugated copper phthalocyanine polymer (CuPcP) is the same as step (1) of Example 1, except that anhydrous NiCl2 is replaced with an equimolar amount of anhydrous CuCl2.

[0093] In this embodiment, the preparation method of the electrode used for electrochemical ammonia synthesis is the same as step (2) of Example 1, except that NiPcP powder is replaced with an equal weight of CuPcP powder.

[0094] The electrode for electrochemical ammonia synthesis provided in Example 2 was used to test the electrocatalytic ammonia synthesis performance. The specific methods and test results are as follows:

[0095] An H-type electrolytic cell was used, with the electrode prepared in Example 2 for electrochemical ammonia synthesis as the working electrode, Hg / HgO as the reference electrode, and a carbon rod as the counter electrode. The electrolyte was 1.0 mol / L KOH + 1.0 mol / L KNO3 (pH = 14). Argon gas was purged for 30 min before electrolysis to remove dissolved oxygen. Electrolysis was performed at a constant potential of -0.8 V (vs. RHE) for 2 h on a CHI760E electrochemical workstation. After electrolysis, a certain amount of electrolyte was taken, and the NH4+ was determined using the indophenol blue method. + The concentration was calculated to be FE 77.6%, and the ammonia yield was 25.1 gh. -1 g cat -1 .

[0096] Example 3

[0097] This embodiment provides an electrode for the electrochemical synthesis of ammonia.

[0098] The electrode includes a conductive substrate and a two-dimensional conjugated copper-nickel phthalocyanine polymer (CuNiPcP) loaded on the conductive substrate. The structure of the two-dimensional conjugated copper-nickel phthalocyanine polymer (CuNiPcP) includes a metal-nitrogen coordination center as shown in formula (Ⅰ) above, wherein M1, M2, M3 and M4 include at least copper and nickel.

[0099] In this embodiment, the preparation method of the two-dimensional conjugated copper-nickel phthalocyanine polymer (CuNiPcP) is the same as step (1) of Example 1, except that anhydrous NiCl2 is replaced with an equimolar amount of anhydrous CuCl2 and anhydrous NiCl2, wherein the molar ratio of CuCl2 and NiCl2 is 1:1.

[0100] In this embodiment, the preparation method of the electrode used for electrochemical ammonia synthesis is the same as step (2) of Example 1, except that NiPcP powder is replaced with an equal weight of CuNiPcP powder.

[0101] The electrode for electrochemical ammonia synthesis provided in Example 3 was used to test the electrocatalytic ammonia synthesis performance. The specific methods and test results are as follows:

[0102] An H-type electrolytic cell was used, with the electrode prepared in Example 3 for electrochemical ammonia synthesis as the working electrode, Hg / HgO as the reference electrode, and a carbon rod as the counter electrode. The electrolyte was 1.0 mol / L KOH + 1.0 mol / L KNO3. Argon gas was purged for 30 min before electrolysis to remove dissolved oxygen. Electrolysis was performed at a constant potential of -0.8 V (vs. RHE) for 2 h on a CHI760E electrochemical workstation. After electrolysis, a certain amount of electrolyte was taken, and NH4+ was determined using the indophenol blue method. + The concentration was calculated to yield an FE of 92.8% and an ammonia yield of 32.8 gh.-1 g cat -1 .

[0103] Example 4

[0104] This embodiment provides an electrode for denitrification treatment of wastewater and / or exhaust gas. The electrode includes a conductive substrate and a two-dimensional conjugated copper-nickel phthalocyanine polymer (CuNiPcP) loaded on the conductive substrate. The structure of the two-dimensional conjugated copper-nickel phthalocyanine polymer (CuNiPcP) includes a metal-nitrogen coordination center as shown in formula (I) above, wherein M1, M2, M3 and M4 include at least copper and nickel.

[0105] Actual wastewater simulation tests were conducted using the electrode for wastewater and / or waste gas denitrification treatment provided in Example 4, as follows:

[0106] Configuration of simulated agricultural runoff wastewater containing nitrates: NO3 - Concentration 0.05 mol / L, also contains Cl - (0.01 mol / L), SO4 2- (0.005 mol / L), HCO3 - (0.01 mol / L) plasma. Electrolysis was performed at -0.7 V vs. RHE using an electrode designed for wastewater and / or exhaust gas denitrification as the working electrode.

[0107] The test results showed that the FE remained above 90%, and the ammonia yield was 91% of the theoretical value. Inductively coupled plasma mass spectrometry (ICP-MS) analysis of the electrolyzed solution showed no Ni ion dissolution.

[0108] This demonstrates that the electrode provided in this embodiment for denitrification of wastewater and / or exhaust gas exhibits good selectivity and stability for actual wastewater systems with complex ionic compositions, and has practical application potential.

[0109] Comparative Example 2

[0110] This comparative example provides an electrode for electrochemical ammonia synthesis and its preparation method. Referring to Example 1, the difference is that in step (1) of this comparative example, the heat treatment temperature is 200℃, and the prepared two-dimensional conjugated nickel phthalocyanine polymer is denoted as NiPcP-200.

[0111] The electrocatalytic ammonia synthesis performance of the electrode prepared in Comparative Example 2 was tested according to the method of Example 1. The electrochemical test results showed that the NiPcP-200 sample prepared at 200℃ had an electrochemical efficiency (FE) of 80.0% and an ammonia yield of 4.3 gh. -1 g cat -1 .

[0112] Comparative Example 3

[0113] This comparative example provides an electrode for electrochemical ammonia synthesis and its preparation method. Referring to Example 1, the difference is that in step (1) of this comparative example, the heat treatment temperature is 600℃, and the prepared two-dimensional conjugated nickel phthalocyanine polymer is denoted as NiPcP-600.

[0114] The electrocatalytic ammonia synthesis performance of the electrode prepared in Comparative Example 3 was tested according to the method of Example 1. The electrochemical test results showed that the NiPcP-600 sample prepared at 600 °C had an FE of 90.1% and an ammonia yield of 8.6 gh. -1 g cat -1 .

[0115] The test structures of Examples 1, 2, and 3 show that 400℃ is the optimal pyrolysis temperature. At this temperature, the conjugated structure of the nickel phthalocyanine polymer (NiPcP) sample is fully formed without decomposition, and the active site density and conductivity reach an optimal balance. Therefore, it exhibits the best performance (FE = 99.7%, ammonia yield = 14.2 gh). -1 g cat -1 Samples prepared at 200 °C may have insufficient crystallinity, while samples prepared at 600 °C may have partially damaged structures.

[0116] In summary, this application achieves the synergistic effect of multiple effects by constructing a two-dimensional conjugated metal phthalocyanine polymer, thereby comprehensively improving the performance of electrochemical ammonia synthesis:

[0117] 1. Structural effect: Two-dimensional conjugate network and high-density M-N4 sites.

[0118] (1) Theoretical basis: Two-dimensional conjugated structures can form extended electronic conduction pathways through π-π stacking, which can greatly improve the intrinsic conductivity of the material and promote the rapid transfer of charge from the electrode to the active site.

[0119] (2) Structural characterization evidence: Taking two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) as an example, Figure 8 The XRD patterns of the nickel phthalocyanine monomer (NiPc) in Comparative Example 1 and the two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) in Example 1 are shown. Figure 8 It can be seen that the (200) peak of the two-dimensional conjugated nickel phthalocyanine polymer shifts to a higher angle, indicating that its interlayer packing is more compact, which is conducive to in-plane electron conduction.

[0120] (3) Performance correlation: Taking two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) as an example, Figure 9 The electrochemical impedance spectroscopy spectra of the nickel phthalocyanine monomer (NiPc) in Comparative Example 1 and the nickel phthalocyanine polymer (NiPcP) in Example 1 of this application are shown. Figure 9 It is evident that the lower charge transfer resistance (EIS) and higher double-layer capacitance (Cdl) confirm the advantages of charge transport and active area.

[0121] 2. Electronic effect: The d-band center shifts upward and becomes an electron-rich metal center.

[0122] (1) Theoretical basis: According to the d-band center theory, the d-band center position of a transition metal is relative to the Fermi level (E). f The adsorption strength of the d-band is determined by its position on the reaction intermediate. The center of the d-band shifts upward (closer to E). f This usually enhances the adsorption of intermediates, thereby promoting multi-step proton-electron transfer processes.

[0123] (2) Experimental evidence: Taking two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) as an example, Figure 10 This diagram shows a comparison of the Ni 2p ratios of the nickel phthalocyanine monomer (NiPc) in Comparative Example 1 and the nickel phthalocyanine polymer (NiPcP) in Example 1 of this application. Figure 10 It can be seen that the XPS Ni 2p binding energy of the two-dimensional conjugated nickel phthalocyanine polymer shifts downward and the valence band spectrum E VB The upward shift indicates an increase in the electron density at the Ni center and an upward shift in the Ni 3d orbital energy level.

[0124] (3) Performance correlation: Taking two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) as an example, density functional theory (DFT) calculations show that the d-band center of NiPcP (-2.5 eV) is higher than that of NiPc monomer (-2.73 eV), and the NO3⁻ adsorption energy is lower (1.27 eV vs. 1.69 eV), which confirms that it has a stronger adsorption and activation ability for nitrates and their intermediates.

[0125] 3. Interface effect: hydrophobic microenvironment and mass transfer regulation.

[0126] (1) Theoretical basis: Hydrophobic surfaces can inhibit the contact and activation of water molecules on the surface of two-dimensional conjugated metal phthalocyanine polymers, thereby effectively suppressing HER side reactions. At the same time, hydrophobic interfaces are conducive to the desorption of gaseous reactants (such as generated NH3), avoiding the blockage of active sites caused by product accumulation.

[0127] (2) Experimental evidence: Taking nickel phthalocyanine polymer (NiPcP) as an example, Figure 11 A comparison diagram of the contact angles of the nickel phthalocyanine monomer (NiPc) in Comparative Example 1 and the nickel phthalocyanine polymer (NiPcP) in Example 1 of this application is shown, as follows: Figure 11 As shown, NiPcP (138°) is more hydrophobic than the nickel phthalocyanine monomer NiPc (127°).

[0128] (3) Performance correlation: Taking the nickel phthalocyanine polymer (NiPcP) provided in Example 1 as an example, it can still maintain high FE under a wide potential window, indicating that HER is effectively suppressed; it can still maintain high activity under low concentration of nitrate, indicating that the hydrophobic interface may be beneficial to the enrichment of low concentration reactants on the catalyst surface.

[0129] 4. Synergistic effect: The structure, electrons, and interface work together. The two-dimensional conjugated structure not only provides a highly conductive framework, but its unique nitrogen-bridged tetraisoindole structure also creates a hydrophobic microenvironment and regulates the electronic state of the metal center. This achieves a triple synergy of "structure promoting conductivity, interface suppressing side reactions, and strong electron adsorption", which is the fundamental reason for achieving high activity under wide operating conditions.

[0130] The electrode for electrochemical ammonia synthesis and its application in electrochemical ammonia synthesis provided in this application have the following significant advantages and advancements compared to existing technologies:

[0131] 1. Highly efficient catalytic performance: The highest FE (Extraction Fe) of the two-dimensional conjugated nickel phthalocyanine polymer (NiPcP) is 99.7%, and the highest ammonia yield of the two-dimensional conjugated copper nickel phthalocyanine polymer (CuNiPcP) is 32.8 gh. -1 g cat -1 .

[0132] 2. Wide operating condition performance: Ultra-high Faraday efficiency (>80%) was achieved on non-precious metal-based catalysts within a wide potential window and a wide nitrate concentration range, solving the core problem of catalyst sensitivity to operating condition fluctuations.

[0133] 3. Clear structure-activity relationship and design strategy: Through a combination of experiments and theoretical calculations, the synergistic mechanism of the three factors of "two-dimensional conjugated structure → high conductivity / high specific surface area", "electron-rich center → strong intermediate adsorption" and "hydrophobic interface → inhibition of HER" was clearly elucidated, providing a clear molecular engineering guide for the design of electrodes for electrochemical ammonia synthesis.

[0134] 4. Excellent overall performance indicators: While achieving high FE (99.7%) and high ammonia yield, it also has excellent long-term stability (48 hours) and good practical wastewater treatment potential. All performance indicators are balanced and leading.

[0135] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An electrode for electrochemical synthesis of ammonia, characterized in that, The electrode for electrochemical ammonia synthesis comprises a conductive substrate and a two-dimensional conjugated metal phthalocyanine polymer supported on the conductive substrate, wherein the structure of the two-dimensional conjugated metal phthalocyanine polymer contains a metal-nitrogen coordination center as shown in formula (I); Equation (I); Among them, M1, M2, M3 and M4 are each independently selected from any one of nickel, iron, copper, cobalt, zinc and manganese.

2. The electrode for electrochemical ammonia synthesis according to claim 1, characterized in that, The conductive substrate includes at least one of carbon cloth, carbon paper, nickel foam, nickel mesh, iron mesh, and stainless steel mesh.

3. The application according to claim 1, characterized in that, The two-dimensional conjugated metal phthalocyanine polymer was loaded at a concentration of 0.1 mg / cm² on the conductive substrate. 2 ~ 5.0 mg / cm 2 .

4. The electrode for electrochemical ammonia synthesis according to claim 1, characterized in that, The two-dimensional conjugated metal phthalocyanine polymer has a mesoporous structure.

5. The electrode for electrochemical ammonia synthesis according to any one of claims 1 to 4, characterized in that, The two-dimensional conjugated metal phthalocyanine polymer was prepared by the following method: The mixture of transition metal salt and 1,2,4,5-tetracyanobenzene was heat-treated in a vacuum or inert atmosphere, and then washed and dried to obtain the two-dimensional conjugated metal phthalocyanine polymer. Wherein, the molar ratio of the transition metal salt to the 1,2,4,5-tetracyanobenzene is (1:1) ~ (1:3). The heat treatment temperature is 200℃ ~ 600℃, and the heat treatment time is 2 h ~ 6 h.

6. The electrode for electrochemical ammonia synthesis according to claim 5, characterized in that, The transition metal salt includes at least one of anhydrous nickel salt, anhydrous iron salt, anhydrous ferrous salt, anhydrous copper salt, anhydrous cobalt salt, anhydrous zinc salt, and anhydrous manganese salt.

7. The electrode for electrochemical ammonia synthesis according to claim 6, characterized in that, The nickel salt includes at least one of anhydrous nickel chloride, anhydrous nickel nitrate, anhydrous nickel acetate, and anhydrous nickel sulfate; The iron salt includes at least one of anhydrous ferric chloride, anhydrous ferric nitrate, anhydrous ferric acetate, and anhydrous ferric sulfate; The ferrous salt includes at least one of anhydrous ferrous chloride, anhydrous ferrous nitrate, anhydrous ferrous acetate, and anhydrous ferrous sulfate. The copper salt includes at least one of anhydrous copper chloride, anhydrous copper nitrate, anhydrous copper acetate, and anhydrous copper sulfate; The cobalt salt includes at least one of anhydrous cobalt chloride, anhydrous cobalt nitrate, anhydrous cobalt acetate, and anhydrous cobalt sulfate; The zinc salt includes at least one of anhydrous zinc chloride, anhydrous zinc nitrate, anhydrous zinc acetate, and anhydrous zinc sulfate; The manganese salt includes at least one of anhydrous manganese chloride, anhydrous manganese nitrate, anhydrous manganese acetate, and anhydrous manganese sulfate.

8. An apparatus for electrochemical synthesis of ammonia, characterized in that, The apparatus for electrochemical ammonia synthesis includes: The electrode for electrochemical synthesis of ammonia according to any one of claims 1 to 7; an electrolytic cell; and an electrolyte located in the electrolytic cell, the electrolyte containing a nitrogen source.

9. The apparatus for electrochemical ammonia synthesis according to claim 8, characterized in that, The electrolytic cell is an H-type electrolytic cell or a flow electrolytic cell; The nitrogen source includes at least one of nitrate, nitrite, nitrogen dioxide, nitric oxide, nitrous oxide, and nitrogen gas. The pH of the electrolyte is 1 to 14; The operating potential of the electrochemical ammonia synthesis apparatus is 0.0 ~ -1.5 V; When the nitrogen source includes nitrate and / or nitrite, the concentration of nitrate and / or nitrite is 1.0 mmol / L to 5.0 mol / L.

10. An electrode for denitrification treatment of wastewater and / or waste gas, characterized in that, The electrode includes a conductive substrate and a two-dimensional conjugated metal phthalocyanine polymer loaded on the conductive substrate, wherein the structure of the two-dimensional conjugated metal phthalocyanine polymer contains a metal-nitrogen coordination center as shown in formula (I); Equation (I); Among them, M1, M2, M3 and M4 are each independently selected from any one of nickel, iron, copper, cobalt, zinc and manganese.

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