A catalyst for efficient electrocatalytic reduction of nitrate to synthesize hydroxylamine

Abstract

The application discloses a catalyst for efficiently electrocatalytically reducing nitrate to synthesize hydroxylamine. The catalyst is composed of a heterostructure of Bi-MoO x The application establishes an electrochemical reaction system composed of an electrode material prepared based on the catalyst, a reaction electrolyte and an electrolytic cell, and applies the system to a reaction of electrocatalytically reducing nitrate to synthesize hydroxylamine mediated by a ketone. The catalyst realizes high Faraday efficiency and cyclohexanone conversion rate at a high current in the applied reaction, can efficiently synthesize hydroxylamine, and has a simple and economical preparation process with industrialization potential, so that the catalyst and the electrode material are convenient for large-scale production and have industrialization potential, and the application provides an alternative scheme for realizing green synthesis of hydroxylamine.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering, and specifically relates to a catalyst for the efficient electrocatalytic reduction of nitrates to synthesize hydroxylamine. Background Technology

[0002] In modern production, pesticide and fertilizer residues and industrial wastewater contain large amounts of nitrogen-containing pollutants, especially nitrogen oxides (NOx). x Nitrogenous pollutants (usually existing in the form of nitrates and nitrites) have become major nitrogenous pollutants in water bodies. These pollutants not only damage the environment, leading to eutrophication and soil compaction, but also affect human health, causing diseases such as methemoglobinemia. Electrochemical methods can be used to remove nitrates (NO3) from wastewater. - (This is) converted into high-value products, namely electrocatalytic NO3. - Reduction reaction (NO3RR) has also become a feasible green conversion solution.

[0003] Hydroxylamine (NH2OH), as an important nitrogen source and highly reactive compound, has wide applications in industrial and agricultural production, pharmaceuticals, and other fields. Traditional industrial methods for synthesizing hydroxylamine include the Raschig process and nitric oxide (NO) reduction. The former requires highly corrosive and polluting sulfur dioxide (SO2) as a reducing agent, while the latter relies on noble metal catalysts and high-purity hydrogen (H2) to reduce NO. Furthermore, in these traditional methods, the nitrogen source is derived from the oxidation of ammonia (NH3), a step requiring noble metal catalysts at high temperatures, and the ammonia is obtained from the energy-intensive Haber–Bosch process. These factors lead to severe carbon emissions, energy consumption, and environmental pollution problems associated with traditional industrial synthesis methods. Therefore, electrochemical methods are of great significance as a green alternative for synthesizing hydroxylamine.

[0004] In numerous studies, hydroxylamine intermediates ( NH2OH) is considered to be an intermediate present in the electrocatalytic NO3RR process, however NH₂OH is very unstable and readily reduces to ammonia, making it difficult to directly obtain hydroxylamine. Studies have shown that cyclohexanone (C₆H₂O) is more susceptible to this. 10 O) can capture the NO3-generated NO3- in situ during the electrocatalytic NO3RR process. NH2OH undergoes CN coupling to generate cyclohexanone oxime (C6H2O). 11 NO), while cyclohexanone oxime can release hydroxylamine through a simple hydrolysis step, therefore using cyclohexanone as the mediator molecule is a feasible route for the electrocatalytic reduction of nitrate to synthesize hydroxylamine. Besides Besides the instability of NH2OH, this process also faces the following challenges: NO3 - The reduction process requires active hydrogen ( H) Participation, H is mainly produced by the activation of H2O, therefore H2O and NO3 - The mismatch between adsorption and activation will lead to Insufficient or excessive hydrogen (H) can decrease the yield of cyclohexanone oxime or enhance the hydrogen evolution reaction (HER). Therefore, the catalyst designed for this reaction needs to be matched with H2O and NO3. - Simultaneous inhibition of adsorption and activation NH2OH is further reduced. Summary of the Invention

[0005] The purpose of this invention is to provide a catalyst for the efficient electrocatalytic reduction of nitrates to synthesize hydroxylamine.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a catalyst for the efficient electrocatalytic reduction of nitrates to synthesize hydroxylamine.

[0008] The catalyst is composed of Bi-MoO x Composed of heterogeneous structures.

[0009] Furthermore, x can take the value 2. <x<3。

[0010] The catalyst is prepared by a method comprising the following steps: 1) Disperse the bismuth compound and surfactant in deionized water and stir to form a suspension. Add sodium molybdate (Na2MoO4) to the suspension and continue stirring. Transfer the mixed solution to a hydrothermal reactor and carry out a hydrothermal reaction to obtain precursor 1. 2) The precursor 1 is heated at high temperature in a tube furnace under an argon atmosphere to obtain the precursor 2; 3) The precursor 2 is subjected to in-situ electrochemical reduction in an electrolyte to obtain the catalyst.

[0011] In step 1) of the above method, the bismuth compound is selected from at least one of bismuth nitrate (Bi(NO3)3), bismuth chloride (BiCl3), bismuth sulfate (Bi2(SO4)3), bismuth bromide (BiBr3), bismuth iodide (BiI3), bismuth citrate (C6H5BiO7) and their hydrates, specifically bismuth nitrate pentahydrate.

[0012] In step 1) of the above method, the surfactant is selected from at least one of hexadecyltrimethylammonium bromide (CTAB) and hexadecyltrimethylammonium chloride (CTAC), specifically CTAB.

[0013] In step 1) of the above method, the molar ratio of the bismuth compound to the surfactant is (1-10):1, specifically 5:1.

[0014] In step 1) of the above method, the dispersion is carried out by magnetic stirring, and the stirring speed can be 300-800 r·min. -1 Specifically, it can be 600 r·min -1 The stirring time can be 0.1-3 h, specifically 1 h.

[0015] In step 1) of the above method, the molar ratio of the bismuth compound and sodium molybdate can be 1:10-10:1, further 1:1-4:1, specifically 2:1, 4:1, or 1:1.

[0016] In step 1) of the above method, the hydrothermal reaction temperature can be 120-200 ℃, specifically 160 ℃; the hydrothermal reaction time can be 6-72 h, specifically 12 h.

[0017] In step 1) of the above method, after the hydrothermal reaction is completed, the following steps are also included: centrifuging to collect the product, and washing and drying it.

[0018] Furthermore, the centrifugation speed can be 4000-12000 rpm, specifically 8000 rpm, and the time can be 1-60 min, specifically 5 min; Furthermore, the washing solvent may be at least one of deionized water, ethanol, acetone and methanol, specifically deionized water and ethanol; Furthermore, the drying can be vacuum drying, with a vacuum drying temperature of 30-100 ℃, specifically 60 ℃, and a drying time of 6-72 h, specifically 12 h; In step 2) of the above method, the heating temperature of the tubular furnace can be 150-600 ℃, specifically 450 ℃; the heating rate of the tubular furnace can be 1-20 ℃·min. -1 Specifically, it can be 5 ℃·min -1 The heating time for a tubular furnace can be 0.5-3 hours, specifically 1 hour.

[0019] In step 3) of the above method, the electrolyte can be at least one of KOH aqueous solution, NaOH aqueous solution, K2CO3 aqueous solution, Na2CO3 aqueous solution, KHCO3 aqueous solution, NaHCO3 aqueous solution, K2SO4 aqueous solution, and Na2SO4 aqueous solution; specifically, it can be KOH aqueous solution.

[0020] In step 3) of the above method, the concentration of the electrolyte can be 0.01-2 mol·L⁻¹. -1Specifically, it can be 1 mol·L -1 .

[0021] In step 3) of the above method, the potential applied for electrochemical reduction can be -0.5 to -2 V vs. RHE, specifically -1 V vs. RHE.

[0022] In step 3) of the above method, the electrochemical reduction time can be 1-30 min, specifically 10 min.

[0023] In step 3) of the above method, the in-situ electrochemical reduction uses an H-type electrolytic cell, with precursor 2 drop-coated onto carbon fiber paper as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum mesh electrode as the counter electrode.

[0024] Secondly, the present invention provides an electrode material.

[0025] The electrode material provided by this invention is composed of the above-mentioned Bi-MoO x It consists of a heterogeneous catalyst and carbon fiber paper.

[0026] The electrode material can be prepared by a method including the following steps: dispersing the precursor 2 and Nafion dispersion in an organic solvent, drop-coating the resulting dispersion onto carbon fiber paper, and performing in-situ electrochemical reduction to obtain the electrode material.

[0027] Furthermore, in the above method, the organic solvent can be selected from at least one of ethanol, isopropanol, acetone, and methanol, specifically isopropanol.

[0028] Furthermore, in the above method, the Nafion dispersion is a perfluorosulfonic acid resin (PFSA) alcohol-water dispersion system with a mass fraction of 5%-20%.

[0029] Furthermore, the Nafion dispersion may specifically be a Nafion D-521CS dispersion with a mass fraction of 5%.

[0030] Furthermore, in the above method, the ratio of the Nafion dispersion to the precursor 2 can be 0.5-10 μL:1 mg, specifically 1 μL:1 mg.

[0031] Furthermore, in the above method, the dispersion is carried out under ultrasonic conditions, and the dispersion time can be 1-30 minutes, specifically 10 minutes.

[0032] Furthermore, in the above method, the amount of precursor 2 can be 0.1-5 mg·cm³. -2 Specifically, it can be 1 mg·cm -2 .

[0033] Furthermore, in the above method, the potential applied for the in-situ electrochemical reduction can be -0.5 to -2 V vs. RHE, specifically -1 V vs. RHE; the time for the in-situ electrochemical reduction can be 1-30 min, specifically 10 min.

[0034] Furthermore, in the above method, the electrolyte used for the in-situ electrochemical reduction can be at least one of KOH aqueous solution, NaOH aqueous solution, K2CO3 aqueous solution, Na2CO3 aqueous solution, KHCO3 aqueous solution, NaHCO3 aqueous solution, K2SO4 aqueous solution, and Na2SO4 aqueous solution; specifically, it can be KOH aqueous solution; the concentration of the electrolyte can be 0.01-2 mol·L⁻¹. -1 Specifically, it can be 1 mol·L -1 .

[0035] Furthermore, in the above method, the in-situ electrochemical reduction uses an H-type electrolytic cell, with precursor 2 drop-coated onto carbon fiber paper as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum mesh electrode as the counter electrode.

[0036] Thirdly, the present invention provides an electrochemical reaction system.

[0037] The electrochemical reaction system uses the electrode material described in the third aspect as the working electrode, and also includes a reaction electrolyte and a reaction device.

[0038] The reaction electrolyte may be selected from at least one of the following: an aqueous solution containing cyclohexanone and KNO3; an aqueous solution containing cyclohexanone, KHCO3 and KNO3; an aqueous solution containing cyclohexanone, KOH and KNO3; an aqueous solution containing cyclohexanone and NaNO3; an aqueous solution containing cyclohexanone, NaHCO3 and NaNO3; or an aqueous solution containing cyclohexanone, NaOH and NaNO3.

[0039] The concentration of cyclohexanone in the reaction electrolyte can be 0.01-1 mol·L⁻¹. -1 The concentration of KNO3 can be 0.1-2 mol·L⁻¹ -1 The concentration of KHCO3 can be 0.1-2 mol·L⁻¹ -1 The concentration of KOH can be 0.1-2 mol·L⁻¹. -1 The concentration of NaNO3 can be 0.1-2 mol·L⁻¹ -1 The concentration of NaHCO3 can be 0.1-2 mol·L⁻¹ -1 The concentration of NaOH can be 0.1-2 mol·L⁻¹ -1 Specifically, the reaction electrolyte can be 0.05 mol·L⁻¹. -1Cyclohexanone and 1 mol·L -1 A mixed aqueous solution of KNO3.

[0040] The reaction apparatus is an H-type electrolytic cell, in which a Nafion 117 proton exchange membrane is used to separate the anode and cathode.

[0041] Fourthly, the present invention provides applications of the catalyst described in the first aspect, the electrode material described in the third aspect, and the electrochemical reaction system.

[0042] The application is its use in the ketone-mediated conductive catalytic reduction of nitrate to synthesize hydroxylamine.

[0043] In one embodiment, cyclohexanone and nitrate are used as raw materials, and in the above-mentioned electrochemical reaction system, Bi-MoO is used... x Cyclohexanone oxime was synthesized by constant current electrolysis using a heterogeneous catalyst and electrolyte. After the reaction, hydrochloric acid or sulfuric acid was added to the electrolyte to hydrolyze the cyclohexanone oxime to produce hydroxylamine. The electrolyte used in the reaction was 0.05 mol·L⁻¹. -1 Cyclohexanone and 1 mol·L -1 A mixed solution of KNO3; The above-mentioned electrode material is used as the working electrode, the Ag / AgCl electrode is used as the reference electrode, and the platinum mesh electrode is used as the counter electrode.

[0044] The reaction current is -50 to -130 mA, specifically -90 mA; The reaction time is 0.5-100 h, specifically 6 h.

[0045] Fifthly, the present invention provides a method for synthesizing hydroxylamine by ketone-mediated electric catalytic reduction of nitrate.

[0046] The method for synthesizing hydroxylamine by ketone-mediated electric catalytic reduction of nitrates provided by the present invention includes the following steps: Using cyclohexanone and nitrate as raw materials, in the electrochemical reaction system, through Bi-MoO x Cyclohexanone oxime is synthesized by constant current electrolysis using a heterogeneous catalyst and electrolyte. After the reaction, hydrochloric acid or sulfuric acid is added to the electrolyte to hydrolyze the cyclohexanone oxime to produce hydroxylamine.

[0047] Furthermore, the electrolyte is 0.05 mol·L⁻¹. -1 Cyclohexanone and 1 mol·L -1 A mixed solution of KNO3.

[0048] Furthermore, the reaction current of the constant current electrolysis reaction is -50 to -130 mA, specifically -90 mA.

[0049] Furthermore, the reaction time of the constant current electrolysis reaction is 0.5-100 h, specifically 6 h.

[0050] This invention proposes a Bi-MoO x Heterogeneous catalysts and their application in the ketone-mediated conductive catalytic reduction of nitrates to hydroxylamine. This catalyst can efficiently catalyze the above reaction in an H-type electrolyzer, achieving a Faradaic efficiency of 43% for the main product cyclohexanone oxime and a cyclohexanone conversion rate of 98%. Hydrolysis of cyclohexanone oxime can yield hydroxylamine with near 100% conversion. The catalyst of this invention can achieve high Faradaic efficiency and conversion rates at relatively high reaction currents, showing potential for industrial application. Furthermore, the catalyst of this invention utilizes NO3, a common pollutant in wastewater. - As a nitrogen source, it provides a feasible and environmentally friendly alternative route for the synthesis of hydroxylamine, which is of great significance in reducing energy consumption and improving environmental pollution. Attached Figure Description

[0051] Figure 1 for Bi-MoO x Scanning electron microscope (SEM) image at -2°C; Figure 2 for Bi-MoO x -2 High-resolution transmission electron microscopy (HRTEM) images; Figure 3 for Bi-MoO x -2 element distribution map (EDS Mapping); Figure 4 X-ray diffraction (XRD) patterns of different catalysts; Figure 5 for Bi-MoO x X-ray photoelectron spectroscopy (XPS) at -2; Figure 6 The graph shows the Faraday efficiency versus conversion rate for different catalysts. Figure 7 for Bi-MoO x -2 Faraday efficiency versus conversion rate at different currents. Detailed Implementation

[0052] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0053] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0054] Example 1: Preparation and characterization of the catalyst: Bi-MoO x Taking the preparation of catalyst -2 as an example.

[0055] First, 2 mmol of Bi(NO3)3·5H2O and 0.4 mmol of CTAB were added to 35 mL of deionized water and stirred until evenly dispersed. Then, 1 mmol of Na2MoO4·2H2O was added to the suspension, and stirring was continued for 1 h. The resulting suspension was placed in a 50 mL hydrothermal reactor, which was then placed in an explosion-proof oven and kept at 160 °C for 12 h. After naturally cooling to room temperature, the precipitate was obtained by centrifugation at 8000 rpm for 5 min. After washing repeatedly with ethanol and deionized water, the precipitate was dried in a vacuum drying oven at 60 °C for 12 h to obtain precursor 1. Precursor 1 was then placed in a tube furnace, purged with argon gas, and heated at 450 °C for 1 h to obtain precursor 2.

[0056] Subsequently, 10 mg of precursor 2 was mixed with 10 μL of Nafion D-521CS dispersion (5% by mass) and dispersed in 1 mL of isopropanol. The mixture was sonicated for 10 min to ensure uniform dispersion. The dispersion was then evenly drop-coated onto the surface of carbon fiber paper and dried using infrared lamp irradiation. The loading of precursor 2 on each electrode was 1 mg·cm³. -2 The precursor electrode was subjected to in-situ electrochemical reduction at -1 V vs. RHE using an H-type electrolytic cell, with an Ag / AgCl electrode as the reference electrode and a platinum mesh as the counter electrode. The electrolyte was 1 mol·L⁻¹. -1 The reduction was carried out with KOH aqueous solution for 10 min, eventually yielding Bi-MoO. x -2 Catalyst electrode.

[0057] Based on the above method, by adjusting the amount of Na₂MoO₄·2H₂O added to 0 mmol, 0.5 mmol, and 2 mmol, respectively, Bi and Bi-MoO₄ were obtained. x -1 and Bi-MoO x -3 Catalyst electrode.

[0058] We studied Bi-MoO x The catalyst was systematically characterized, and scanning electron microscopy (SEM) revealed Bi-MoO₂.x -2 exhibits a nanoparticle morphology ( Figure 1 The lattice fringe spacing in high-resolution transmission electron microscopy (HRTEM) is 0.322 nm, which can be attributed to the (012) crystal plane of Bi. Figure 2 The elemental distribution map (EDS Mapping) shows the elements Bi, Mo, and O in Bi-MoO. x -2 Catalyst surface uniformly distributed ( Figure 3 The molar ratio of Bi to Mo in different catalysts was quantitatively determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). X-ray diffraction (XRD) analysis showed that Bi-MoO x -2 The catalyst contains only the Bi crystal phase ( Figure 4 X-ray photoelectron spectroscopy (XPS) analysis showed that Bi-MoO x -2 The oxidation states of Mo on the catalyst surface are +4 and +5, and the oxidation states of Bi are 0 and +3. Figure 5 Combining the results of EDS and XPS, it is believed that the Mo species are dominated by MoO. x The form exists, but MoO is not shown in TEM and XRD. x The crystal characteristics may be due to the low Mo content and the presence of MoO on it. x Most of them are amorphous.

[0059] Example 2: Application of catalysts in the ketone-mediated electrochemical synthesis of hydroxylamine: Using the Bi-MoO described in Example 1 x The catalyst electrode was used as the working electrode, and all electrochemical experiments were performed on a multichannel electrochemical workstation (CS310X, Wuhan Koster Instruments Co., Ltd.). Electrolysis experiments were conducted at 25℃ using a 30 mL three-electrode H-type electrolytic cell system. The three electrodes included the aforementioned working electrode, an Ag / AgCl reference electrode, and a platinum mesh counter electrode. A Nafion 117 proton exchange membrane separated the cathode and anode. Both the cathode and anode chambers were heated to 0.05 mol·L⁻¹. -1 Cyclohexanone + 1 mol·L -1 The KNO3 aqueous solution was used as the electrolyte, with a volume of 30 mL. The current range during the test was -50 to -130 mA, and the electrolysis time was 6 h.

[0060] Product analysis: Cyclohexanone oxime was analyzed by gas chromatography (GC, Agilent 7890B), and other liquid products were detected by UV-Vis spectrophotometer (UV-vis, T9S, Beijing Purkinje General Instrument Co., Ltd.).

[0061] Different MoOx The content of catalysts for the electrocatalysis of cyclohexanone and NO3 - The experimental results of the reaction (reaction current was -90 mA) are as follows: Figure 6 As shown; Electrocatalytic reaction of cyclohexanone and NO3 under different current conditions - The experimental results of the reaction are as follows Figure 7 As shown in the figure, the catalyst of this invention exhibits excellent selectivity for cyclohexanone oxime, compared to other materials, Bi-MoO₂. x The catalyst with a current of -2 exhibits the best catalytic performance, achieving a Faradaic efficiency of 43% for cyclohexanone oxime (CHO) at a current of -90 mA, with a cyclohexanone conversion rate of 97.4%. Adding sulfuric acid to the electrolyte after the reaction hydrolyzes the cyclohexanone oxime, converting it to hydroxylamine with a near 100% conversion rate.

[0062] The present invention has been described in detail above. For those skilled in the art, the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. Although specific embodiments have been given, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein. Some of the essential features can be applied within the scope of the following appended claims.

Claims

1. A catalyst for the highly efficient electrocatalytic reduction of nitrates to synthesize hydroxylamine, comprising Bi-MoO₂ x Composed of heterogeneous structures.

2. The catalyst according to claim 1, characterized in that: The preparation method of the catalyst includes the following steps: 1) Dispersing bismuth compound and surfactant in deionized water and stirring to form a suspension, adding sodium molybdate (Na2MoO4) to the suspension and continuing to stir, transferring the mixed solution to a hydrothermal reactor and carrying out a hydrothermal reaction to obtain precursor 1; 2) The precursor 1 is heated at high temperature in a tube furnace under an argon atmosphere to obtain the precursor 2; 3) The precursor 2 is subjected to in-situ electrochemical reduction in an electrolyte to obtain the catalyst.

3. The catalyst according to claim 2, characterized in that: In step 1), the bismuth compound is selected from at least one of bismuth nitrate (Bi(NO3)3), bismuth chloride (BiCl3), bismuth sulfate (Bi2(SO4)3), bismuth bromide (BiBr3), bismuth iodide (BiI3), bismuth citrate (C6H5BiO7), and their hydrates. And / or, in step 1), the surfactant is selected from at least one of hexadecyltrimethylammonium bromide (CTAB) and hexadecyltrimethylammonium chloride (CTAC); And / or, in step 1), the molar ratio of the bismuth compound to the surfactant is (1-10):1; And / or, in step 1), the molar ratio of the bismuth compound to sodium molybdate is 1:10-10:1, or more specifically 1:1-4:1; And / or, in step 1), the hydrothermal reaction temperature is 120-200 ℃; the hydrothermal reaction time is 6-72 h.

4. The catalyst according to claim 2 or 3, characterized in that: In step 2), the heating temperature of the tubular furnace is 150-600 ℃; the heating time of the tubular furnace is 0.5-3 h. And / or, in step 3), the electrolyte is at least one of KOH aqueous solution, NaOH aqueous solution, K2CO3 aqueous solution, Na2CO3 aqueous solution, KHCO3 aqueous solution, NaHCO3 aqueous solution, K2SO4 aqueous solution, and Na2SO4 aqueous solution; And / or, in step 3), the electrolyte concentration is 0.01-2 mol·L⁻¹. -1 ; And / or, in step 3), the potential applied for the electrochemical reduction is -0.5 to -2 V vs. RHE; And / or, in step 3), the electrochemical reduction time is 1-30 min; And / or, in step 3), the in-situ electrochemical reduction uses an H-type electrolytic cell, with precursor 2 drop-coated onto carbon fiber paper as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum mesh electrode as the counter electrode.

5. An electrode material, comprising Bi-MoO as described in any one of claims 1-4 x It consists of a heterogeneous catalyst and carbon fiber paper.

6. The electrode material according to claim 5, characterized in that: The electrode material is prepared by a method comprising the following steps: dispersing the precursor 2 and Nafion dispersion as described in claim 1 in an organic solvent, drop-coating the resulting dispersion onto carbon fiber paper, and performing in-situ electrochemical reduction to obtain the electrode material.

7. The electrode material according to claim 6, characterized in that: The organic solvent is selected from at least one of ethanol, isopropanol, acetone, and methanol; And / or, the Nafion dispersion is a perfluorosulfonic acid resin (PFSA) alcohol-water dispersion system with a mass fraction of 5%-20%; And / or, the ratio of the Nafion dispersion to the precursor 2 is 0.5-10 μL:1 mg; And / or, the dosage of precursor 2 is 0.1-5 mg·cm³. -2 ; And / or, the potential applied for the in-situ electrochemical reduction can be -0.5 to -2 V vs. RHE, and the time for the in-situ electrochemical reduction is 1-30 min; And / or, the electrolyte used in the in-situ electrochemical reduction is at least one of KOH aqueous solution, NaOH aqueous solution, K2CO3 aqueous solution, Na2CO3 aqueous solution, KHCO3 aqueous solution, NaHCO3 aqueous solution, K2SO4 aqueous solution, and Na2SO4 aqueous solution; And / or, the in-situ electrochemical reduction uses an H-type electrolytic cell, with precursor 2 drop-coated onto carbon fiber paper as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum mesh electrode as the counter electrode.

8. An electrochemical reaction system, using the electrode material of any one of claims 5-7 as the working electrode, further comprising an electrolyte and a reaction apparatus.

9. The electrochemical reaction system according to claim 8, characterized in that: The reaction electrolyte is selected from at least one of the following: an aqueous solution containing cyclohexanone and KNO3; an aqueous solution containing cyclohexanone, KHCO3 and KNO3; an aqueous solution containing cyclohexanone, KOH and KNO3; an aqueous solution containing cyclohexanone and NaNO3; an aqueous solution containing cyclohexanone, NaHCO3 and NaNO3; and an aqueous solution containing at least one of cyclohexanone, NaOH and NaNO3. The concentration of cyclohexanone in the electrolyte is 0.01-1 mol·L⁻¹. -1 The concentration of KNO3 is 0.1-2 mol·L⁻¹ -1 The concentration of KHCO3 is 0.1-2 mol·L⁻¹ -1 The concentration of KOH is 0.1-2 mol·L⁻¹. -1 The concentration of NaNO3 is 0.1-2 mol·L⁻¹ -1 The concentration of NaHCO3 is 0.1-2 mol·L⁻¹ -1 The concentration of NaOH is 0.1-2 mol·L⁻¹ -1 ; The reaction apparatus is an H-type electrolytic cell, in which a Nafion 117 proton exchange membrane is used to separate the anode and cathode.

10. A method for synthesizing hydroxylamine by ketone-mediated electric catalytic reduction of nitrate, comprising the following steps: Using cyclohexanone and nitrate as raw materials, in the electrochemical reaction system described in claim 8 or 9, through Bi-MoO x Cyclohexanone oxime is synthesized by constant current electrolysis reaction using a heterogeneous catalyst and electrolyte. After the reaction, hydrochloric acid or sulfuric acid is added to the electrolyte to hydrolyze cyclohexanone oxime to produce hydroxylamine. Furthermore, the reaction current of the constant current electrolysis reaction is -50 to -130 mA; Furthermore, the reaction time of the constant current electrolysis reaction is 0.5-100 h.

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