An organic phosphate group functionalized nanoarray electrode and its preparation method and application

Abstract

The present invention relates to the field of electrocatalytic electrode technology, specifically to an organophosphate group-functionalized nanoarray electrode and its preparation method and application, the method comprising the steps of: dissolving a nickel salt and an organic ligand in a mixed solvent to prepare a mixed solution, wherein the organic ligand is composed of terephthalic acid and terephthalic acid, and the mixed solvent is composed of a mixture of N,N-dimethylformamide, water and ethanol; placing the mixed solution and an electrode substrate in a reactor together, sealing and performing a solvent thermal reaction, and after the reaction is completed, the reactor is naturally cooled to room temperature, the electrode substrate is removed and washed and vacuum dried to prepare an organophosphate group-functionalized nanoarray electrode. The present invention can significantly increase the rate of ammonia synthesis by in-situ self-assembly of a uniform and highly dispersed nickel-based nanoarray on the electrode substrate; the present invention also regulates the electronic structure of the nickel center through organophosphate group functionalization, thereby achieving a high ammonia synthesis Faraday efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic electrodes, and in particular to an organic phosphoric acid group functionalized nanometer array electrode and a preparation method and application thereof. Background Art

[0002] Ammonia is the world's second-largest basic chemical, widely used in the manufacture of fertilizers, pharmaceuticals, and fuels. Furthermore, its zero-carbon, high energy density, high hydrogen content, and ease of storage make it a potential green energy carrier and fuel.

[0003] However, traditional ammonia synthesis processes require high temperatures (-500°C) and high pressures (>100 atm). According to statistics, the ammonia synthesis industry accounts for 1-2% of global energy consumption and emits approximately 2% of total greenhouse gases. Furthermore, with the rapid development of industry and agriculture, the discharge of large amounts of nitrate-containing industrial wastewater, domestic sewage, and agricultural wastewater poses a serious threat to the ecological environment and human health.

[0004] Electrocatalytic nitrate reduction to ammonia synthesis not only achieves resource utilization of waste, but also alleviates the environmental problems caused by the synthetic ammonia industry. It is of great significance in solving both energy and environmental problems. At the same time, electrocatalytic nitrate reduction to ammonia synthesis technology has the advantages of not requiring the addition of chemical agents, mild reaction conditions, and is expected to be completely driven by renewable energy. The core foundation of electrocatalytic reduction technology is cathode materials. However, most of the catalysts reported so far have complex preparation steps and are in powder form. When used, they need to be loaded onto the electrode substrate with a binder, which greatly increases the operating cost.

[0005] Furthermore, electrocatalytic nitrate reduction to ammonia is a proton-coupled electron transfer (PCET) process involving the transfer of eight electrons and nine protons. Therefore, the efficiency of proton transfer near the catalytically active center significantly influences catalyst performance. Recent studies have shown that organophosphate groups possess excellent proton conductivity. However, technologies that utilize organophosphate groups to promote proton transfer for efficient nitrate-to-ammonia synthesis have not been reported.

[0006] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0007] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide an organophosphate group-functionalized nanoarray electrode and its preparation method and application, aiming to solve the problems of harsh preparation conditions and complex application process of existing electrocatalytic nitrate reduction catalysts for ammonia synthesis.

[0008] The technical solutions of the present invention are as follows:

[0009] A method for preparing an organophosphate group-functionalized nanoarray electrode, comprising the steps of:

[0010] Dissolving a nickel salt and an organic ligand in a mixed solvent to prepare a mixed solution, wherein the organic ligand is composed of terephthalic acid and terephthalic diphosphoric acid, and the mixed solvent is composed of a mixture of N,N-dimethylformamide, water and ethanol;

[0011] The mixed solution and the electrode matrix are placed in a reactor together, sealed and subjected to solvent thermal reaction. After the reaction is completed, the reactor is naturally cooled to room temperature, the electrode matrix is ​​taken out and washed and vacuum-dried to obtain an organophosphate group-functionalized nanoarray electrode.

[0012] The method for preparing the organophosphate group-functionalized nanoarray electrode, wherein the nickel salt is one or more of nickel chloride, nickel nitrate and nickel sulfate; and the concentration of the nickel salt is 0.01-0.5 mol / L.

[0013] The method for preparing the organic phosphoric acid group functionalized nanoarray electrode, wherein the molar ratio of terephthalic acid to terephthalic diphosphate in the organic ligand is 1:0.1-10.

[0014] The method for preparing the organic phosphoric acid group functionalized nanoarray electrode, wherein the molar ratio of the nickel salt to the organic ligand is 1:0.1-10.

[0015] The method for preparing the organic phosphoric acid group functionalized nanoarray electrode, wherein the volume ratio of N,N-dimethylformamide, water and ethanol in the mixed solvent is 1:(0.01-0.1):(0.01-0.1).

[0016] The method for preparing the organophosphate group functionalized nanoarray electrode, wherein the electrode substrate is foamed nickel, foamed titanium or carbon felt.

[0017] In the method for preparing the organophosphate group functionalized nanoarray electrode, in the step of performing a solvent thermal reaction after sealing, the reaction temperature is 100-150° C. and the reaction time is 5-24 hours.

[0018] In the method for preparing the organophosphate group functionalized nanoarray electrode, in the steps of removing the electrode substrate and washing and vacuum drying, the vacuum drying temperature is 30-80° C. and the time is 12-24 hours.

[0019] An organic phosphoric acid group functionalized nanometer array electrode is prepared by adopting the preparation method of the organic phosphoric acid group functionalized nanometer array electrode of the present invention.

[0020] An application of an organophosphate group-functionalized nanometer array electrode, wherein the organophosphate group-functionalized nanometer array electrode of the present invention is used for electrocatalytic nitrate reduction to synthesize ammonia.

[0021] Beneficial effects: The present invention loads uniform and highly dispersed nickel-based nanoarrays on the electrode substrate through in-situ self-assembly, significantly increasing the active area of ​​the electrode and promoting the mass transfer of nitrate to the catalytic active sites, thereby greatly improving the rate of ammonia synthesis; the present invention also regulates the electronic structure of the nickel center through functionalization of organic phosphate groups, thereby improving the electron transfer rate from protons to the nickel center during the electrocatalytic process and achieving high Faraday efficiency for ammonia synthesis; the present invention prepares large-area, highly active self-supporting nanoarray electrodes through a one-step method, the reaction conditions are easy to control, the raw materials are easily available, and the preparation cost is low. The prepared organic phosphate group-functionalized nanoarray electrodes can achieve efficient and highly selective transfer of pollutant nitrate to ammonia, and have good prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of the preparation method of an organophosphate group functionalized nanoarray electrode provided by the present invention.

[0023] Figure 2 This is a scanning electron microscope photograph of the electrode obtained in Example 1 of the present invention.

[0024] Figure 3 This is the element distribution diagram of the electrode obtained in Example 1 of the present invention.

[0025] Figure 4 This is the element content spectrum of the electrode obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The present invention provides an organophosphate group-functionalized nanoparticle array electrode, its preparation method, and application. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0027] See also Figure 1 , Figure 1 The present invention provides a flow chart of a method for preparing an organophosphate group-functionalized nanoarray electrode, as shown in the figure, which includes the following steps:

[0028] S10, dissolving the nickel salt and the organic ligand in a mixed solvent to prepare a mixed solution, wherein the organic ligand is composed of terephthalic acid and terephthalic diphosphate, and the mixed solvent is composed of a mixture of N,N-dimethylformamide, water and ethanol;

[0029] S20, placing the mixed solution and the electrode matrix together in a reaction kettle, sealing it and performing a solvent thermal reaction. After the reaction is completed, the reaction kettle is naturally cooled to room temperature, the electrode matrix is ​​taken out and washed and vacuum-dried to obtain an organophosphate group-functionalized nanoarray electrode.

[0030] Specifically, the present invention utilizes a one-step in situ self-assembly process to load uniformly sized and highly dispersed nickel-based nanoarrays onto an electrode substrate. Simultaneously, the electronic structure of the nickel centers is optimized by regulating the organophosphate ligands. This nickel-based nanoarray structure not only significantly increases the cathode's active area but also facilitates mass transfer of nitrate ions to the catalytically active sites, thereby significantly increasing the rate of ammonia synthesis. Furthermore, the organophosphate groups enhance the rate of proton transfer to the nickel centers during the electrocatalytic process, achieving a high Faradaic efficiency for ammonia synthesis. Coupling the organophosphate-functionalized nanoarray electrode prepared by the present invention with a platinum anode and conducting the electrocatalytic nitrate reduction reaction in an electrolytic cell separated by a proton exchange membrane enables efficient and highly selective conversion of the pollutant nitrate to ammonia. This invention addresses the harsh preparation conditions and complex application processes of existing electrocatalytic nitrate reduction catalysts for ammonia synthesis. It also proposes a strategy for enhancing the proton transfer rate through organophosphate groups, thereby significantly improving the rate and Faradaic efficiency of electrocatalytic nitrate reduction for ammonia synthesis.

[0031] In some embodiments, the electrode substrate is nickel foam, titanium foam, or carbon felt, but is not limited thereto. The electrode substrate needs to be pretreated before the reaction. Specifically, the electrode substrate is ultrasonically cleaned in a 0.005-0.01 mol / L hydrochloric acid solution for 10-30 minutes, then ultrasonically cleaned in acetone or ethanol for 0.5-1 hour, and finally rinsed with ultrapure water until no acetone or ethanol remains, and then used.

[0032] In some embodiments, the nickel salt is one or more of nickel chloride, nickel nitrate, and nickel sulfate; the concentration of the nickel salt is 0.01-0.5 mol / L, preferably 0.25 mol / L.

[0033] In some embodiments, in the organic ligand, the molar ratio of terephthalic acid to terephthalic diphosphoric acid is 1:0.1-10, preferably 1:0.1.

[0034] In some embodiments, the molar ratio of the nickel salt to the organic ligand is 1:0.1-10, preferably 1:1.

[0035] In some embodiments, in the mixed solvent, the volume ratio of N,N-dimethylformamide, water and ethanol is 1:(0.01-0.1):(0.01-0.1), preferably 1:0.05:0.05.

[0036] In some embodiments, in the step of performing the solvothermal reaction after sealing, the reaction temperature is 100-150° C., and the reaction time is 5-24 h.

[0037] In some embodiments, in the steps of removing the electrode substrate and performing washing and vacuum drying, the electrode substrate is first washed with N,N-dimethylformamide for 0.5-1 hour, then washed with ethanol for 0.5-1 hour, and finally washed with pure water for 0.5-1 hour; then the vacuum drying temperature is 30-80°C and the time is 12-24 hours.

[0038] In some embodiments, an organophosphate group-functionalized nanoarray electrode is further provided, wherein the electrode is prepared using the method for preparing the organophosphate group-functionalized nanoarray electrode of the present invention.

[0039] The present invention uses in-situ self-assembly to load a uniform and highly dispersed nickel-based nanoarray on the electrode substrate, significantly increasing the active area of ​​the electrode and promoting the mass transfer of nitrate to the catalytic active site, thereby greatly improving the rate of ammonia synthesis. The present invention also regulates the electronic structure of the nickel center through functionalization of organic phosphoric acid groups, thereby improving the electron transfer rate of protons to the nickel center during the electrocatalytic process and achieving a high Faraday efficiency for ammonia synthesis. The present invention uses a one-step method to prepare a large-area, highly active self-supporting nanoarray electrode. The reaction conditions are easy to control, the raw materials are readily available, and the preparation cost is low. The prepared organic phosphoric acid group-functionalized nanoarray electrode can achieve efficient and highly selective transfer of the pollutant nitrate to ammonia, and has good prospects for industrial application.

[0040] In some embodiments, an application of an organophosphate group-functionalized nanoarray electrode is also provided, wherein the organophosphate group-functionalized nanoarray electrode of the present invention is used to electrocatalyze nitrate reduction to synthesize ammonia.

[0041] The present invention will be further explained below by means of specific embodiments:

[0042] Example 1

[0043] This embodiment provides a method for preparing an organophosphate group-functionalized nanoarray electrode: nickel foam (2 cm*4 cm*1 mm) is ultrasonically cleaned in a 0.01 mol / L hydrochloric acid solution for 30 minutes, then ultrasonically cleaned with anhydrous ethanol for 30 minutes, and finally cleaned with ultrapure water until no ethanol residue is left. 5 mmol of nickel nitrate hexahydrate, 4.5 mmol of terephthalic acid, and 0.5 mmol of terephthalic acid are dissolved in a mixed solvent of 18 mL of N,N-dimethylformamide, 1 mL of ethanol, and 1 mL of water. The mixed solvent and the pretreated nickel foam are placed in a reactor, sealed, and reacted at 130° C. for 5 hours. After the reaction is completed, the reactor is naturally cooled to room temperature, and the electrode is removed. The resulting electrode is first cleaned with N,N-dimethylformamide for 30 minutes, then with ethanol for 30 minutes, and finally with pure water for 30 minutes. The cleaned electrode is vacuum-dried at 80° C. for 24 hours.

[0044] As attached Figure 2 The morphology of the electrode obtained in this embodiment is that the nickel foam skeleton is loaded with a uniform and highly dispersed nanoarray, indicating that a uniform nanoarray structure is formed after in-situ self-assembly; at the same time, the attached Figure 3 In the element distribution diagram, phosphorus is evenly dispersed on the nanosheets, indicating that the organic phosphate groups are involved in the coordination of the nanosheet structure; Figure 4 The element content spectrum proves that the electrode has been successfully introduced with organophosphate groups.

[0045] This example also provides the application of the above-prepared organophosphate group-functionalized nanoarray electrode to the electrocatalytic reduction of nitrate to synthesize ammonia: using the obtained electrode as the cathode, platinum wire as the anode, Nafion 117 proton exchange membrane as the diaphragm, and mercury / mercuric oxide electrode as the reference electrode, a three-electrode system is used for electrocatalysis at a constant voltage of -1.3V vs Hg / HgO; wherein the concentration of KNO3 is 1 mol / L, the cathode compartment electrolyte is a 1 mol / L KOH solution, and the anode compartment electrolyte is a 1 mol / L Na2SO4 solution, and the solution volume is 30 mL. The effect of the electrode obtained in this example on the electrocatalytic reduction of nitrate to synthesize ammonia is shown in Table 1.

[0046] Example 2

[0047] This embodiment provides a method for preparing an organophosphate group-functionalized nanoarray electrode: nickel foam (2 cm*4 cm*1 mm) is ultrasonically cleaned in a 0.01 mol / L hydrochloric acid solution for 30 minutes, then ultrasonically cleaned with anhydrous ethanol for 30 minutes, and finally cleaned with ultrapure water until no ethanol residue is left. 5 mmol of nickel sulfate hexahydrate, 4 mmol of terephthalic acid, and 1 mmol of terephthalic acid are dissolved in a mixed solvent of 18 mL of N,N-dimethylformamide, 1 mL of ethanol, and 1 mL of water. The mixed solvent and the pretreated nickel foam are placed in a reactor, sealed, and reacted at 120° C. for 8 hours. After the reaction is completed, the reactor is naturally cooled to room temperature, and the electrode is removed. The resulting electrode is first cleaned with N,N-dimethylformamide for 30 minutes, then with ethanol for 30 minutes, and finally with pure water for 30 minutes. The cleaned electrode is vacuum-dried at 80° C. for 18 hours.

[0048] This example also provides an application of the organophosphate functionalized nanoarray electrode prepared above: the application of this electrode is the same as that in Example 1. The effect of the electrode obtained in this example on electrocatalytic nitrate reduction to synthesize ammonia is shown in Table 1.

[0049] Example 3

[0050] This embodiment provides a method for preparing an organophosphate group-functionalized nanoarray electrode: nickel foam (2 cm*4 cm*1 mm) is ultrasonically cleaned in a 0.01 mol / L hydrochloric acid solution for 30 minutes, then ultrasonically cleaned with anhydrous ethanol for 30 minutes, and finally cleaned with ultrapure water until no ethanol residue is left. 5 mmol of nickel chloride hexahydrate, 3 mmol of terephthalic acid, and 2 mmol of terephthalic acid are dissolved in a mixed solvent of 18 mL of N,N-dimethylformamide, 1 mL of ethanol, and 1 mL of water. The mixed solvent and the pretreated nickel foam are placed in a reactor, sealed, and reacted at 130° C. for 10 hours. After the reaction is completed, the reactor is naturally cooled to room temperature, and the electrode is removed. The resulting electrode is first cleaned with N,N-dimethylformamide for 30 minutes, then with ethanol for 30 minutes, and finally with pure water for 30 minutes. The cleaned electrode is vacuum-dried at 80° C. for 20 hours.

[0051] This example also provides an application of the organophosphate functionalized nanoarray electrode prepared above: the application of this electrode is the same as that in Example 1. The effect of the electrode obtained in this example on electrocatalytic nitrate reduction to synthesize ammonia is shown in Table 1.

[0052] Comparative Example 1

[0053] This comparative example provides a method for preparing a nickel-based nanoarray electrode: the preparation method of the electrode is basically the same as that of Example 1, the only difference being that the amount of terephthalic acid added is 0.

[0054] This comparative example also provides an application of the nickel-based nanoarray electrode prepared above: the application of this electrode is the same as that in Example 1. The effect of the electrode obtained in this comparative example on electrocatalytic nitrate reduction to synthesize ammonia is shown in Table 1.

[0055] Table 1 shows the performance of electrocatalytic nitrate synthesis of ammonia in Examples 1-3 and Comparative Examples.

[0056]

[0057] As can be seen from the data in Table 1, under the same voltage conditions, the ammonia synthesis rates of Examples 1-3 were significantly higher than those of Comparative Example 1, and the Faradaic efficiencies of Examples 1-3 were also significantly higher than those of Comparative Example 1. This demonstrates that the in situ self-assembly of uniform and highly dispersed nickel-based nanoarrays onto the electrode substrate significantly increases the electrode active area, promoting mass transfer from nitrate to the catalytic active sites, thereby significantly increasing the ammonia synthesis rate. It also demonstrates that functionalization with organophosphate groups and regulation of the electronic structure of the nickel center can enhance the electron transfer rate from protons to the nickel center during the electrocatalytic process, thereby achieving high Faradaic efficiencies for ammonia synthesis.

[0058] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing an organophosphate functionalized nanoarray electrode, characterized in that: Including steps: Dissolving a nickel salt and an organic ligand in a mixed solvent to prepare a mixed solution, wherein the organic ligand is composed of terephthalic acid and terephthalic diphosphoric acid, and the mixed solvent is composed of a mixture of N,N-dimethylformamide, water and ethanol; The mixed solution and the electrode matrix are placed in a reactor together, sealed and subjected to solvent thermal reaction. After the reaction is completed, the reactor is naturally cooled to room temperature, the electrode matrix is ​​taken out and washed and vacuum-dried to obtain an organophosphate group-functionalized nanoarray electrode.

2. The method for preparing the organophosphate functionalized nanoarray electrode according to claim 1, characterized in that: The nickel salt is one or more of nickel chloride, nickel nitrate and nickel sulfate; and the concentration of the nickel salt is 0.01-0.5 mol / L.

3. The method for preparing the organophosphate functionalized nanoarray electrode according to claim 1, characterized in that: In the organic ligand, the molar ratio of terephthalic acid to terephthalic diphosphoric acid is 1:0.1-10.

4. The method for preparing the organophosphate functionalized nanoarray electrode according to claim 1, characterized in that: The molar ratio of the nickel salt to the organic ligand is 1:0.1-10.

5. The method for preparing the organophosphate functionalized nanoarray electrode according to claim 1, characterized in that: In the mixed solvent, the volume ratio of N,N-dimethylformamide, water and ethanol is 1:(0.01-0.1):(0.01-0.1).

6. The method for preparing the organophosphate functionalized nanoarray electrode according to claim 1, characterized in that: The electrode substrate is foamed nickel, foamed titanium or carbon felt.

7. The method for preparing the organophosphate functionalized nanoarray electrode according to claim 1, characterized in that: In the step of performing solvent thermal reaction after sealing, the reaction temperature is 100-150° C. and the reaction time is 5-24 hours.

8. The method for preparing the organophosphate functionalized nanoarray electrode according to claim 1, characterized in that: In the steps of taking out the electrode substrate and performing washing and vacuum drying, the vacuum drying temperature is 30-80° C. and the time is 12-24 hours.

9. An organophosphate functionalized nanoarray electrode, characterized in that: The nanoparticles are prepared by the method for preparing the organophosphate group-functionalized nanoarray electrode according to any one of claims 1 to 8.

10. An application of an organophosphate functionalized nanoarray electrode, characterized in that: The organophosphate group-functionalized nanoarray electrode according to claim 9 is used for electrocatalytic nitrate reduction to synthesize ammonia.

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