Cuprous oxide-based electrocatalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electrocatalysis, and particularly relates to a cuprous oxide-based electrocatalyst as well as a preparation method and application thereof. The cuprous oxide-based electrocatalyst comprises a conductive substrate and a cuprous oxide active layer loaded on the surface of the conductive substrate, the cuprous oxide active layer has a nano sheet shape; the cuprous oxide active layer is used for generating a corresponding saturated product from a nitrogen heterocyclic ring organic compound through electrochemical hydrogenation.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis technology, and particularly relates to a cuprous oxide-based electrocatalyst, its preparation method, and its application. Background Technology

[0002] Against the backdrop of the global pursuit of carbon neutrality and sustainable development, hydrogen energy, as a clean energy carrier with high energy density, wide availability, and a combustion product consisting only of water, is considered the core of the future energy system. However, hydrogen is gaseous at room temperature and pressure, and its storage and transportation face severe challenges such as high-pressure explosiveness and high energy consumption during low-temperature liquefaction. Liquid organic hydrogen storage carrier (LOHC) technology, through reversible hydrogenation / dehydrogenation reactions, stores hydrogen in liquid molecules in the form of chemical bonds, achieving safe and efficient room-temperature and atmospheric-pressure storage and transportation of hydrogen energy, and is one of the most promising solutions.

[0003] In LOHC technology, nitrogen-containing heterocyclic organic compounds (such as pyrazines and quinoxalines) have attracted much attention due to their high hydrogen storage density and good stability. Electrocatalytic hydrogenation of unsaturated liquid organic compounds to generate saturated hydrogen-rich products is a key step in realizing hydrogen energy "storage." The core of this process lies in developing high-performance cathode electrocatalysts. Currently, research mainly focuses on noble metal catalysts (such as platinum and palladium) and some non-noble metal catalysts (such as cobalt-based and nickel-based materials). Although noble metal catalysts have high activity, their scarcity and high cost severely restrict their large-scale commercial application. While non-noble metal catalysts are cheaper, they generally suffer from insufficient catalytic activity, require high overpotentials to drive the reaction, have poor product selectivity, and exhibit poor stability in electrolytes.

[0004] Therefore, there is an urgent need in this field to develop a novel electrocatalyst for the electrocatalytic hydrogenation of nitrogen-containing heterocyclic organic compounds. This catalyst needs to possess both high catalytic activity and high product selectivity, effectively reducing reaction energy consumption. Simultaneously, its preparation method should be simple, low-cost, and easily scalable. The catalyst itself should exhibit excellent physical and chemical stability, be able to bond firmly to a conductive substrate, and ensure that its performance does not significantly degrade during long-term electrochemical reactions, thereby meeting the requirements of industrial applications. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a cuprous oxide-based electrocatalyst, its preparation method, and its application.

[0006] Firstly, a cuprous oxide-based electrocatalyst employs the following technical solution: A cuprous oxide-based electrocatalyst includes a conductive substrate and a cuprous oxide active layer supported on the surface of the conductive substrate; the cuprous oxide active layer has a nanosheet morphology; the cuprous oxide active layer is used to generate corresponding saturated products from nitrogen-containing heterocyclic organic compounds via electrochemical hydrogenation.

[0007] Furthermore, the conductive substrate is selected from one of nickel foam, carbon paper, carbon felt, cobalt foam, and copper foam.

[0008] Furthermore, the conductive substrate is nickel foam.

[0009] Secondly, a method for preparing a cuprous oxide-based electrocatalyst employs the following technical solution: A method for preparing a cuprous oxide-based electrocatalyst includes the following steps: An aqueous solution containing a copper soluble salt, ammonium fluoride, and urea is subjected to a hydrothermal reaction with a conductive substrate under closed conditions to generate a precursor on the conductive substrate. The conductive substrate with the precursor attached is calcined in an oxygen-containing atmosphere to obtain the cuprous oxide-based electrocatalyst.

[0010] Furthermore, the hydrothermal reaction is carried out at a temperature of 110℃-120℃ for 6h-8h; the calcination is carried out at a temperature of 400℃-500℃ for 3h-5h.

[0011] Thirdly, the application of a cuprous oxide-based electrocatalyst employs the following technical solution: Application of a cuprous oxide-based catalyst in the hydrogenation reaction of nitrogen-containing heterocyclic organic compounds, wherein the cuprous oxide-based electrocatalyst is used as the cathode of the electrocatalytic hydrogenation reaction.

[0012] Furthermore, in the hydrogenation reaction, the electrolyte in the cathode chamber comprises a strong alkaline aqueous solution of ≤3 mol / L and the nitrogen-containing heterocyclic organic compound at a concentration of ≤0.5 mol / L.

[0013] Furthermore, a platinum or carbon electrode is used as the anode for the electrocatalytic hydrogenation reaction, and the electrolyte in the anode chamber contains a strong alkaline aqueous solution of ≤10 mol / L.

[0014] Furthermore, the nitrogen-containing heterocyclic organic compound is selected from one or more of pyrazine, quinoxaline and their derivatives.

[0015] Furthermore, the nitrogen-containing heterocyclic organic compound is a pyrazine, and its corresponding saturated product is a piperazine.

[0016] The beneficial effects of this invention are: This invention provides a cuprous oxide-based electrocatalyst. By employing cuprous oxide with a nanosheet morphology as the active layer and directly loading it onto a conductive substrate, this catalyst, with copper as its core, replaces traditional precious metal catalysts, significantly reducing material costs and laying an economic foundation for industrial applications. The nanosheet morphology increases the specific surface area and the number of active sites of the catalyst, significantly improving the catalytic activity and current density for the electrocatalytic hydrogenation of nitrogen-containing heterocyclic organic compounds, effectively reducing the overpotential required for the reaction, thereby reducing overall energy consumption and achieving high product selectivity. The in-situ growth of the active layer on the surface of the conductive substrate forms a binder-free monolithic electrode, ensuring excellent electrical contact and strong physical bonding between the active material and the substrate, preventing the active layer from detaching during the reaction, thus endowing the catalyst with excellent long-term operational stability. This effectively solves the technical problem of simultaneously achieving catalyst activity, selectivity, and stability in existing technologies. Attached Figure Description

[0017] Figure 1 SEM measurements of Cu2O / NF provided in Example 1: (a) 100 μm, (b) 50 μm, (c) 10 μm, (d) 1 μm.

[0018] Figure 2 LSV test was performed with or without 0.01 M pyrazine in 1 M KOH when Cu2O / NF provided in Example 1 was used as the working electrode.

[0019] Figure 3 CV test was performed with or without 0.01 M pyrazine in 1 M KOH when Cu2O / NF provided in Example 1 was used as the working electrode.

[0020] Figure 4 When the working electrode provided in Example 1 is Cu2O / NF, it maintains a constant potential of -0.2 V in the presence of 10 mM pyrazine. vs GC spectrum of RHE hydrogenation reaction after 2 h. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the present application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] In the following description, references to "some embodiments" refer to a subset of all possible embodiments; however, it is understood that "some embodiments" may be the same or different subsets of all possible embodiments and may be combined with each other without conflict. Unless otherwise defined, all technical and scientific terms used in the embodiments of the invention have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of the invention pertain. The terminology used in the embodiments of the invention is for the purpose of describing the embodiments of the invention only and is not intended to limit the invention.

[0023] Those skilled in the art should understand that, in the following description of the embodiments of the present invention, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0024] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0025] Those skilled in the art will understand that the numerical ranges in the embodiments of the present invention should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value and an intermediate value within the stated range, as well as any other stated value or an intermediate value within the stated range, is also included within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in embodiments or test cases of the invention. All references to this specification are generally incorporated herein by reference to disclose and describe methods and / or materials associated with said references. In the event of any conflict with any incorporated reference, the contents of this application shall prevail.

[0027] It should be noted that all raw materials and / or reagents in the embodiments of the present invention were purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0028] This embodiment provides a cuprous oxide-based electrocatalyst, comprising a conductive substrate and a cuprous oxide active layer supported on the surface of the conductive substrate; the cuprous oxide active layer has a nanosheet morphology; the cuprous oxide active layer is used to generate corresponding saturated products from nitrogen-containing heterocyclic organic compounds through electrochemical hydrogenation.

[0029] In some embodiments, the conductive substrate is selected from nickel foam, carbon paper, carbon felt, cobalt foam, and copper foam.

[0030] In some embodiments, the conductive substrate is nickel foam.

[0031] This embodiment provides a high-performance electrocatalyst, the core structure of which is a monolithic electrode. The electrode consists of two parts: a substrate material with good conductivity, and a cuprous oxide layer grown directly in situ on the substrate surface, serving as the catalytic active site. The cuprous oxide active layer exhibits a microscopic morphology of interconnected or independently distributed nanosheets. This three-dimensional, high specific surface area nanosheet morphology maximizes the exposure of catalytic active sites, facilitating the contact of reactant molecules and the desorption of product molecules.

[0032] This electrocatalyst is designed to catalyze the electrochemical hydrogenation of nitrogen-containing heterocyclic organic compounds (such as pyrazines and quinoxalines). By applying a certain potential at the cathode, unsaturated organic compounds are efficiently converted into their corresponding saturated products (such as piperazines). In specific implementations, the choice of conductive substrate is diverse. Materials with three-dimensional porous structures, such as nickel foam (NF), carbon paper (CP), carbon felt, cobalt foam, or copper foam, can be used to provide a larger active material loading area and excellent mass transfer channels. In a preferred embodiment, nickel foam is used as the conductive substrate because it combines excellent conductivity, mechanical strength, and chemical stability in strongly alkaline electrolytes.

[0033] This embodiment provides a method for preparing a cuprous oxide-based electrocatalyst, comprising the following steps: An aqueous solution containing a copper soluble salt, ammonium fluoride, and urea is subjected to a hydrothermal reaction with a conductive substrate under closed conditions to generate a precursor on the conductive substrate. The conductive substrate with the precursor attached is calcined in an oxygen-containing atmosphere to obtain the cuprous oxide-based electrocatalyst.

[0034] In some embodiments, the hydrothermal reaction is carried out at a temperature of 110℃-120℃ for 6h-8h; the calcination is carried out at a temperature of 400℃-500℃ for 3h-5h.

[0035] The preparation process of this catalyst mainly consists of two steps: hydrothermal synthesis and high-temperature calcination, as detailed below: Substrate pretreatment: First, the conductive nickel foam (NF) substrate is cut to a specific size, for example, 2 cm × 3 cm. To remove oil and oxide layers from its surface, it is ultrasonically cleaned sequentially in anhydrous ethanol, 2 M hydrochloric acid aqueous solution, and deionized water for 20 minutes in each liquid. After cleaning, it is removed and rinsed thoroughly with deionized water for later use.

[0036] Hydrothermal reaction: In a 50 mL beaker, deionized water was added, followed by the sequential dissolution of copper nitrate (Cu(NO3)2·6H2O, to a final concentration of 0.08 M), ammonium fluoride (NH4F, to a final concentration of 0.24 M), and urea (to a final concentration of 0.3 M). The mixture was magnetically stirred at room temperature for 40 min until a clear, homogeneous blue solution was formed. This solution was then transferred to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene. A pretreated nickel foam substrate was vertically immersed in the solution. After sealing the autoclave, it was placed in an oven and subjected to a hydrothermal reaction at a constant temperature of 120 °C for 6 h.

[0037] Precursor preparation: After the reaction was completed, the autoclave was allowed to cool naturally to room temperature. The foamed nickel substrate with precipitate was removed and repeatedly rinsed with anhydrous ethanol and deionized water to remove residual ions from the surface. Then it was placed in a vacuum drying oven at 60°C and dried for 8 hours to obtain a conductive substrate loaded with hydroxide / carbonate precursor.

[0038] High-temperature calcination: Finally, the dried substrate loaded with the precursor was placed in a tube furnace and heated to 400°C at a certain rate under air atmosphere, and calcined at this temperature for 3 hours. After calcination, the substrate was allowed to cool naturally to room temperature in the furnace to obtain the final electrocatalyst Cu2O / NF with a nanosheet-like cuprous oxide active layer on its surface.

[0039] This embodiment provides an application of a cuprous oxide-based catalyst in the hydrogenation reaction of nitrogen-containing heterocyclic organic compounds, characterized in that the cuprous oxide-based electrocatalyst is used as the cathode of the electrocatalytic hydrogenation reaction.

[0040] In some embodiments, during the hydrogenation reaction, the electrolyte in the cathode chamber comprises a strong alkaline aqueous solution of ≤3 mol / L and the nitrogen-containing heterocyclic organic compound at a concentration of ≤0.5 mol / L.

[0041] In some embodiments, a platinum electrode or a carbon electrode is used as the anode for the electrocatalytic hydrogenation reaction, and the electrolyte in the anode chamber contains a strong alkaline aqueous solution of ≤3 mol / L.

[0042] In some embodiments, the nitrogen-containing heterocyclic organic compound is selected from one or more of pyrazine, quinoxaline, indole, and their derivatives.

[0043] In some embodiments, the nitrogen-containing heterocyclic organic compound is a pyrazine, and its corresponding saturated product is a piperazine.

[0044] The specific application of this electrocatalyst in the electrocatalytic hydrogenation reaction of nitrogen-containing heterocyclic organic compounds (taking pyrazine as an example) is as follows: Electrochemical reaction apparatus: An H-type electrolytic cell with a glass frit diaphragm was used for electrochemical testing. The cuprous oxide-based electrocatalyst Cu2O / NF prepared in this technical scheme was used as the working electrode (cathode), a platinum (Pt) electrode was used as the counter electrode (anode), and a saturated calomel electrode (SCE) was placed in the cathode chamber as the reference electrode.

[0045] Electrolyte preparation: Cathode chamber electrolyte: 40 mL of electrolyte, which is a mixture of 1 M potassium hydroxide (KOH) aqueous solution and 0.01 M pyrazine, is added to the cathode chamber. The concentrations of the strong base (KOH) and the nitrogen-containing heterocyclic organic compound (pyrazine) are both within the preferred ranges (≤3 mol / L and ≤0.5 mol / L, respectively).

[0046] Anode chamber electrolyte: Add 40 mL of 1 M potassium hydroxide (KOH) aqueous solution to the anode chamber.

[0047] Electrocatalytic hydrogenation reaction: The assembled electrolytic cell is connected to an electrochemical workstation. The hydrogenation reaction is driven by applying a constant negative potential (e.g., -1.25 V vs. SCE) relative to the reference electrode to the cathode (i.e., the Cu₂O / NF catalyst). At this potential, water molecules on the cathode surface are reduced to generate active hydrogen species. These active hydrogen species then react with pyrazine molecules adsorbed on the catalyst surface, hydrogenating and reducing them to piperazine. At the anode, an oxygen evolution reaction occurs to balance the charge. After the reaction has proceeded for a period of time (e.g., 2 hours), an electrolyte sample from the cathode chamber can be taken for component analysis using methods such as gas chromatography (GC) to determine the conversion rate of pyrazine and the selectivity of piperazine.

[0048] The following examples illustrate common substrate pretreatment steps: The conductive substrate was cut to a specific size (actually 2cm × 3cm), and then ultrasonically cleaned for 20 minutes each in anhydrous ethanol, 2M hydrochloric acid, and deionized water to remove surface oil and impurities. It was then dried in a vacuum drying oven at 60℃ for 2 hours for later use.

[0049] Example Example 1 Example 1 provides a cuprous oxide-based electrocatalyst, comprising nickel foam and a cuprous oxide active layer supported on the surface of the nickel foam; the morphology of the cuprous oxide active layer of Example 1 is observed using an electron microscope, as shown below. Figure 1 As shown, its surface exhibits an ellipsoidal nanoneedle-like morphology.

[0050] Example 1 also provides a method for preparing a cuprous oxide-based electrocatalyst, comprising the following steps: Cu(NO3)2·6H2O (0.08 M), NH4F (0.24 M), and urea (0.3 M) were added sequentially to 50 mL of water and magnetically stirred for 40 min to form a homogeneous solution. The solution was transferred to a 100 mL Teflon-lined stainless steel autoclave, and pretreated nickel foam (NF) was vertically immersed into it. The sealed autoclave was placed in a drying oven and heated at 120 °C for 6 h. After the autoclave was cooled to room temperature, the synthesized material was washed with anhydrous ethanol and deionized water and dried in a vacuum drying oven at 60 °C for 8 h to obtain the Cu2O / NF precursor. The precursor was calcined in air at 400 °C for 3 h to obtain the Cu2O / NF catalyst.

[0051] Example 2 Example 2 provides a cuprous oxide-based electrocatalyst, comprising carbon paper and a cuprous oxide active layer supported on the surface of the carbon paper.

[0052] Example 2 also provides a method for preparing a cuprous oxide-based electrocatalyst, comprising the following steps: Cu(NO3)2·6H2O (0.0175 M), NH4F (0.06 M), and urea (0.08 M) were sequentially added to 50 mL of water and magnetically stirred for 40 min to form a homogeneous solution. The solution was then transferred to a 100 mL Teflon-lined stainless steel autoclave, and pretreated carbon paper was vertically immersed in it. The sealed autoclave was placed in a drying oven and heated at 110 °C for 8 h. After the autoclave was cooled to room temperature, the synthesized material was washed with anhydrous ethanol and deionized water and dried in a vacuum drying oven at 60 °C for 8 h to obtain the precursor. The precursor was calcined in air at 400 °C for 3 h to obtain the Cu2O / CP catalyst.

[0053] Example 3 Example 3 provides a cuprous oxide-based electrocatalyst, comprising copper foam and a cuprous oxide active layer supported on the surface of the copper foam.

[0054] Example 3 also provides a method for preparing a cuprous oxide-based electrocatalyst, comprising the following steps: Cu(NO3)2·6H2O (0.225 M), NH4F (0.6 M), and urea (0.8 M) were added sequentially to 50 mL of water and magnetically stirred for 40 min to form a homogeneous solution. The solution was transferred to a 100 mL Teflon-lined stainless steel autoclave, and the pretreated copper foam was vertically immersed in it. The sealed autoclave was placed in a drying oven and heated at 120 °C for 6 h. After the autoclave was cooled to room temperature, the synthesized material was washed with anhydrous ethanol and deionized water and dried in a vacuum drying oven at 60 °C for 8 h to obtain the precursor. The precursor was calcined at 500 °C for 5 h in air to obtain the electrocatalyst.

[0055] Performance testing Electrocatalytic performance testing of Cu2O / NF catalyst for pyrazine hydrogenation Two H-shaped glass electrolytic cells, each with a Nafion 117 proton exchange membrane separating the anode and cathode chambers, were used as the experimental group and the control group, respectively.

[0056] Experimental group: Cathode chamber (working electrode chamber): Add 40.0 mL of electrolyte, which consists of 1.0 M KOH aqueous solution and 0.01 M pyrazine; Anode chamber (counter electrode chamber): Add 40.0 mL of 1.0 M KOH aqueous solution.

[0057] Control group: Cathode chamber (working electrode chamber): Add 40.0 mL of electrolyte, which is composed of 1.0 M KOH aqueous solution; Anode chamber (counter electrode chamber): Add 40.0 mL of 1.0 M KOH aqueous solution.

[0058] Electrode installation and electrochemical testing setup: The Cu2O / NF catalyst prepared in Example 1 was installed as the cathode (working electrode) in two electrolytic cells respectively; platinum sheets were installed as the anode (counter electrode) respectively; and the tip of the Lugin capillary of the saturated calomel electrode (SCE) was placed close to the surface of the working electrode (about 2-3 mm) as the reference electrode in the cathode chamber.

[0059] Connect to the electrochemical workstation. Electrochemical activation: Scan the two sets of electrolytic cells in the range of 0.6 to -0.4V at a rate of 0.05V / s. The results of the linear scan voltammetry test are as follows: Figure 2 As shown, by Figure 2It can be seen that within the range of -0.3 to -0.45 V (vs. SCE), the experimental group with added pyrazine exhibited a higher current density compared to the blank control group without pyrazine, indicating that the hydrogenation reaction dominates within this range. Pyrazine hydrogenation performs better at more negative potentials because the Cu-based component has a very weak promoting effect on H generation; therefore, H can only be generated at higher potentials, leading to the hydrogenation reaction of pyrazine. Cyclic voltammetry (CV) scans were performed several times within the potential range of -0.4 V to -1.4 V (vs. RHE) at a scan rate of 0.05 V / s until the CV curve stabilized. The cyclic voltammetry results are shown below. Figure 3 As shown.

[0060] After activation, a constant potential electrolysis mode was set, and a constant potential of -1.25 V (vs. RHE) was applied to carry out the electrocatalytic hydrogenation reaction of pyrazine for 2 hours. After 2 hours of electrolysis, a small amount of electrolyte sample was carefully removed from the cathode chamber. If necessary, the sample could be diluted with an appropriate solvent (e.g., methanol or a solvent containing an internal standard) and filtered through a 0.22 μm filter membrane to remove solid particles.

[0061] The pretreated sample was injected into a gas chromatograph. The residual amount of pyrazine and the amount of piperazine formed in the reaction solution were quantitatively analyzed by comparing the retention time and peak area with pre-calibrated pyrazine (raw material) and piperazine (main product) standards. The results are as follows: Figure 4 As shown, by Figure 4 It can be seen that after 2 hours of hydrogenation, the piperazine peak appeared at 7.210 min, the pyrazine conversion rate was 10.5%, and the piperazine selectivity was 60.04%, indicating that pyrazine was largely converted into the hydrogenated product piperazine after 2 hours of hydrogenation.

[0062] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A cuprous oxide-based electrocatalyst, characterized in that, It includes a conductive substrate and a cuprous oxide active layer supported on the surface of the conductive substrate; the cuprous oxide active layer has a nanosheet morphology; the cuprous oxide active layer is used to generate corresponding saturated products from nitrogen-containing heterocyclic organic compounds through electrochemical hydrogenation.

2. The cuprous oxide-based electrocatalyst according to claim 1, characterized in that, The conductive substrate is selected from one of the following: nickel foam, carbon paper, carbon felt, cobalt foam, and copper foam.

3. The cuprous oxide-based electrocatalyst according to claim 2, characterized in that, The conductive substrate is nickel foam.

4. A method for preparing a cuprous oxide-based electrocatalyst as described in any one of claims 1 to 3, characterized in that, Includes the following steps: An aqueous solution containing a copper soluble salt, ammonium fluoride, and urea is subjected to a hydrothermal reaction with a conductive substrate under closed conditions to generate a precursor on the conductive substrate. The conductive substrate with the precursor attached is calcined in an oxygen-containing atmosphere to obtain the cuprous oxide-based electrocatalyst.

5. The method according to claim 4, characterized in that, The hydrothermal reaction is carried out at a temperature of 110℃-120℃ for 6h-8h; the calcination is carried out at a temperature of 400℃-500℃ for 3h-5h.

6. The application of a cuprous oxide-based electrocatalyst as described in any one of claims 1 to 3 in the hydrogenation reaction of nitrogen-containing heterocyclic organic compounds, characterized in that, The cuprous oxide-based electrocatalyst is used as the cathode for the electrocatalytic hydrogenation reaction.

7. The application according to claim 6, characterized in that, In the hydrogenation reaction, the electrolyte in the cathode chamber contains a strong alkaline aqueous solution of ≤3 mol / L and the nitrogen-containing heterocyclic organic compound at a concentration of ≤0.5 mol / L.

8. The application according to claim 7, characterized in that, Platinum or carbon electrodes are used as the anode for the electrocatalytic hydrogenation reaction, and the electrolyte in the anode chamber contains a strong alkaline aqueous solution of ≤3 mol / L.

9. The application according to claim 8, characterized in that, The nitrogen-containing heterocyclic organic compound is selected from one or more of pyrazine, quinoxaline and their derivatives.

10. The application according to claim 9, characterized in that, The nitrogen-containing heterocyclic organic compound is a pyrazine, and its corresponding saturated product is a piperazine.

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