Application of copper-cobalt spinel-based composite catalyst in electro-catalysis organic liquid hydrogenation

Abstract

The invention belongs to the technical field of electrochemistry, and particularly relates to application of a copper-cobalt spinel-based composite catalyst in electro-catalysis organic liquid hydrogenation. The invention provides an application of a copper-cobalt spinel-based composite catalyst in electro-catalysis organic liquid hydrogenation. The invention also provides a preparation method of the copper-cobalt spinel-based composite catalyst, which comprises the following steps: dissolving a copper source, a cobalt source, NH4F and urea in water to form a precursor solution; immersing a pretreated inert electrode current collector into the precursor solution, and carrying out hydrothermal reaction to obtain an inert motor current collector attached with a precursor; and calcining the inert motor current collector attached with the precursor in an air atmosphere to obtain the copper-cobalt spinel-based composite catalyst.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical technology, and in particular relates to application of a copper-cobalt spinel-based composite catalyst in electrocatalytic hydrogenation of organic liquids. Background Art

[0002] The selective hydrogenation of organic liquids is an important reaction in the chemical industry, playing a key role in the synthesis of fine chemicals, the preparation of pharmaceutical intermediates, and the emerging liquid organic hydrogen storage carrier (LOHC) technology. For example, the hydrogenation of unsaturated or aromatic nitrogen-containing heterocyclic compounds into saturated cyclic amines is a common step in the synthesis of a variety of drug molecules and agricultural chemicals. At the same time, LOHC technology stores and releases hydrogen through a reversible hydrogenation / dehydrogenation cycle, and is considered to be one of the important ways to achieve large-scale application of hydrogen energy, among which efficient hydrogenation catalysts are the core of this technology. However, many valuable organic liquid hydrogenation reactions often require high selectivity and high conversion under relatively mild conditions, which poses a severe challenge to the design of catalysts. Therefore, the development of efficient, stable and economical catalysts is crucial to promote technological progress and industrial applications in related fields.

[0003] Currently, the most widely used catalysts in the hydrogenation of organic liquids rely primarily on precious metals, such as platinum (Pt), palladium (Pd), ruthenium (Ru), and their alloys or supported catalysts. These precious metal catalysts typically exhibit excellent catalytic activity and good selectivity. However, the scarcity and high cost of precious metal resources significantly limit their application in large-scale industrial production, especially in cost-sensitive areas. To reduce costs, researchers have attempted to improve atomic utilization by reducing the precious metal loading, developing single-atom catalysts, or forming alloys with other metals. However, these approaches often increase the complexity of preparation and do not fundamentally address the cost issue. Therefore, the search for non-precious metal catalysts based on abundant Earth reserves that can replace precious metals and exhibit performance comparable to or even exceeding that of precious metals has become a research hotspot and development direction that urgently needs breakthroughs in this field. Therefore, the development of a catalyst with a simple preparation process, low cost, controllable morphology, and high catalytic activity and selectivity for the hydrogenation of organic liquids is not only of great academic value but also meets the urgent need for low-cost, high-performance catalysts in related industrial applications, potentially overcoming the inherent shortcomings of existing precious metal catalyst systems. Summary of the Invention

[0004] The purpose of the present invention is to solve the above-mentioned deficiencies and provide an application of a copper-cobalt spinel-based composite catalyst in electrocatalytic hydrogenation of organic liquids.

[0005] Application of a copper-cobalt spinel-based composite catalyst in electrocatalytic hydrogenation of organic liquids.

[0006] Furthermore, the organic liquid is a nitrogen-containing heterocyclic organic compound, and the nitrogen-containing heterocyclic organic compound is at least one selected from pyrazine, pyrrole, quinoline and their derivatives containing alkyl groups.

[0007] Furthermore, the electrolyte for electrocatalytic hydrogenation of the organic liquid comprises a strong alkali aqueous solution of 0.5 mol / L to 3.0 mol / L and the organic liquid with a concentration of ≤1.5 mol / L.

[0008] A copper-cobalt spinel-based composite catalyst comprises copper-cobalt spinel and is supported on an inert electrode current collector for use in electrocatalytic hydrogenation of organic liquids.

[0009] Furthermore, the inert electrode current collector is selected from one of nickel foam and carbon paper.

[0010] Furthermore, the copper-cobalt spinel is loaded on an inert electrode current collector and exhibits a spherical nano-needle morphology.

[0011] A method for preparing a copper-cobalt spinel-based composite catalyst comprises the following steps:

[0012] Dissolving a copper source, a cobalt source, NH4F and urea in water to form a precursor solution;

[0013] Immersing the pretreated inert electrode current collector in the precursor solution and performing a hydrothermal reaction to obtain an inert motor current collector with the precursor attached thereto;

[0014] The inert motor current collector with the precursor attached thereto is calcined in an air atmosphere to obtain the copper-cobalt spinel-based composite catalyst.

[0015] Furthermore, the temperature of the hydrothermal reaction is 115° C.-120° C., and the reaction time is 6 h-8 h.

[0016] Furthermore, the calcination temperature is 400° C.-500° C., and the calcination time is 3 h-5 h.

[0017] Furthermore, in the precursor solution, the concentration of the copper source is 0.01mol / L-0.1mol / L, the concentration of the cobalt source is 0.0175mol / L-0.225mol / L, the concentration of NH4F is 0.06mol / L-0.6mol / L, and the concentration of urea is 0.08mol / L-0.8mol / L.

[0018] Beneficial effects of the present invention:

[0019] The application of a copper-cobalt spinel-based composite catalyst provided by the present invention in the electrocatalytic hydrogenation of organic liquids can efficiently catalyze the hydrogenation reaction of organic liquids, thereby effectively replacing the traditional reliance on expensive and resource-scarce precious metal catalysts, significantly reducing the production and use costs of the catalyst, and providing economic feasibility for the large-scale industrial promotion of related hydrogenation processes. In particular, the catalyst exhibits extremely high catalytic activity and excellent reaction conversion ability in this application, and can achieve nearly complete conversion of reactants in a relatively short period of time. Its catalytic efficiency is sufficient to meet the performance indicators of the existing technology, providing a new and highly promising technical approach for achieving efficient, economical and sustainable hydrogenation conversion of organic liquids. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the SEM morphology characterization of the CuCo2O4@NF catalyst prepared in Example 1.

[0021] Figure 2 This is the linear sweep voltammetry test graph of the CuCo2O4@NF catalyst prepared in Example 1 for pyrazine hydrogenation reaction.

[0022] Figure 3 This is a cyclic voltammetry curve test diagram of the CuCo2O4@NF catalyst prepared in Example 1 for pyrazine hydrogenation reaction.

[0023] Figure 4 This is the gas chromatography analysis result of the CuCo2O4@NF catalyst prepared in Example 1 after 2 hours of electrochemical pyrazine hydrogenation.

[0024] Figure 5 This is the gas chromatography analysis result of the CuCo2O4@NF catalyst prepared in Example 1 after 4 hours of electrochemical pyrazine hydrogenation.

[0025] Figure 6 This is the linear sweep voltammetry test graph of the CuCo2O4@NF catalyst prepared in Example 2 for quinoline hydrogenation reaction.

[0026] Figure 7 This is a cyclic voltammetry curve test diagram of the CuCo2O4@NF catalyst prepared in Example 2 for quinoline hydrogenation reaction.

[0027] Figure 8 This is the gas chromatography analysis result of the CuCo2O4@NF catalyst prepared in Example 2 after 2 hours of electrochemical quinoline hydrogenation. DETAILED DESCRIPTION

[0028] The following examples further describe in detail the application of a copper-cobalt spinel-based composite catalyst described in the present invention in the electrocatalytic hydrogenation of organic liquids. For the sake of simplicity of description, this document cannot enumerate all the alternative technical features and implementation plans contained in the present invention. Therefore, those skilled in the art should know that any technical features and implementation plans in this embodiment do not limit the scope of protection of the present invention, which includes any alternative technical features and implementation plans taken by all those skilled in the art without creative work. Specifically, the implementation plans obtained by replacing any technical feature in the present invention or combining any two or more technical features provided by the present invention should be within the scope of protection of the present invention.

[0029] The raw materials and equipment used in the examples are:

[0030] Copper source: analytical grade copper nitrate, analytical grade copper sulfate.

[0031] Cobalt source: analytical grade cobalt nitrate, analytical grade cobalt acetate.

[0032] Auxiliary materials: analytical grade ammonium fluoride, analytical grade urea.

[0033] Electrode substrate: nickel foam (NF), carbon paper (CP).

[0034] Organic liquid materials: analytical grade pyrazine, analytical grade pyrrole, analytical grade quinoline.

[0035] Electrolyte: analytical grade potassium hydroxide (KOH), analytical grade sodium hydroxide (NaOH).

[0036] Other reagents: anhydrous ethanol, hydrochloric acid (HCl), deionized water.

[0037] Equipment: ultrasonic cleaner, magnetic stirrer, stainless steel high-pressure reactor (polytetrafluoroethylene lined), muffle furnace, vacuum drying oven, electrochemical workstation, scanning electron microscope (SEM), gas chromatograph (GC).

[0038] General steps for substrate pretreatment:

[0039] Nickel foam (NF) or carbon paper (CP) substrates were cut into 2 cm x 3 cm dimensions and ultrasonically cleaned in anhydrous ethanol, a 2M hydrochloric acid solution, and deionized water for 15 minutes each to remove surface oil and oxide layers. After cleaning, the substrates were rinsed with deionized water and dried in a vacuum oven at 60°C for 2 hours before use.

[0040] Example

[0041] Example 1

[0042] Example 1 provides a method for preparing a CuCo2O4@NF catalyst, comprising the following steps:

[0043] a) Precursor Solution Preparation: Accurately weigh Cu(NO₃)₂·3H₂O (0.04 M), Co(NO₃)₂·6H₂O (0.08 M, resulting in a Co / Cu molar ratio of 2.0), NH₄F₄ (0.24 M), and urea (0.3 M). Dissolve each of these solids in 50 mL of deionized water, stirring at medium speed with a magnetic stirrer for 30 minutes until a homogeneous, clear solution is formed.

[0044] b) Hydrothermal Reaction: Transfer the entire precursor solution prepared in step a) to a 100 mL stainless steel autoclave with a Teflon-lined interior. Vertically immerse a 2 cm x 3 cm piece of pretreated nickel foam (NF) in the solution. Ensure the NF does not touch the bottom of the autoclave (a Teflon stand can be used). Seal the autoclave and place it in an oven preheated to 120°C. Maintain this temperature for 6 hours.

[0045] c) Precursor post-treatment: After the reaction is completed, allow the reactor to cool naturally to room temperature in an oven. Carefully open the reactor and remove the nickel foam with the product attached. Use tweezers to pick up the nickel foam and rinse it with a large amount of anhydrous ethanol 3-5 times, then rinse it with a large amount of deionized water 3-5 times, alternating to completely remove residual reactants and unreacted ions on the surface. Place the cleaned nickel foam in a clean Petri dish and dry it in a vacuum drying oven at 60°C for 8 hours to obtain the CuCo2O4@NF precursor.

[0046] d) Calcination: Carefully remove the dried precursor (attached to the nickel foam) from the Petri dish and place it in a clean porcelain boat. Place the boat in the central, constant-temperature zone of a muffle furnace. Close the furnace door and program the temperature from room temperature to 400°C at a rate of 5°C / minute, then hold at 400°C for 3 hours. Calcination is performed in an air atmosphere. After calcination, allow the precursor to cool naturally to room temperature. Remove the boat to obtain the black CuCo2O4@NF catalyst.

[0047] The morphology was characterized by scanning electron microscopy (SEM). Figure 1 As shown. Figure 1 The results showed that a microspherical structure composed of a large number of nanoneedle clusters grew evenly and densely on the surface of the three-dimensional skeleton of nickel foam, presenting a typical spherical nanoneedle morphology.

[0048] Example 1 also provides a test of the electrocatalytic hydrogenation performance of a CuCo2O4@NF catalyst for pyrazine:

[0049] a) Electrochemical workstation setup and electrolytic cell assembly: A CHI series electrochemical workstation was used. The H-type electrolytic cell was cleaned and dried. The cathode and anode compartments were separated by a Nafion membrane.

[0050] b) Electrode Installation: Install the prepared CuCo2O4@NF catalyst (effective area calculated based on the actual immersion surface, e.g., 1 cm x 1 cm) as the working electrode in the cathode compartment. Install a platinum sheet (1 cm x 1 cm) as the counter electrode in the anode compartment. Place a saturated calomel electrode (SCE) with the salt bridge tip close to the working electrode surface (approximately 2-3 mm) in the cathode compartment as the reference electrode.

[0051] c) Electrolyte Preparation and Addition: Prepare 40 mL of a 1 M KOH aqueous solution and 40 mL of a 1 M KOH aqueous solution containing 0.04 M pyrazine. Add the 1 M KOH solution containing pyrazine to the cathode compartment, and the 1 M KOH solution without pyrazine to the anode compartment.

[0052] d) Linear voltammetry test: Scan at a rate of 100 mV / s in the potential range of 0 V to -1.5 V (vs. SCE). The linear sweep voltammetry test results are as follows: Figure 2 As shown. Figure 2 The results show that in the range of -1.1--1.3 V, the experimental group with pyrazine added has a higher current density than the blank control group without pyrazine, indicating that the hydrogenation reaction is dominant in this range.

[0053] e) Electrochemical activation: Cyclic voltammetry scans were performed at a rate of 100 mV / s over a potential range of 1.5 V to -1.5 V (vs. SCE) for several cycles until the curve stabilized to activate the electrode surface. The cyclic voltammetry curve test results are shown in Figure 2. Figure 3 As shown. Figure 3 The results show that the CV curve maintains good reversibility after 10 cycles of scanning, indicating that the chemical and mechanical properties of the CuCo2O4@NF electrode are stable during the reaction and the catalyst can provide stable active sites.

[0054] f) Constant-voltage electrolysis: Set the electrochemical workstation to constant-voltage electrolysis mode, apply a constant potential of -1.167 V (vs. SCE), and record the change in current over time.

[0055] g) Product Sampling and Analysis: After 2 and 4 hours of constant-voltage electrolysis, remove a small amount (e.g., 1.0 mL) of the electrolyte sample from the cathode chamber. After appropriate dilution, filtration, and water removal (if necessary), the sample is quantitatively analyzed using a gas chromatograph (GC equipped with an FID detector and a suitable capillary column, such as an HP-5). The pyrazine conversion and piperazine selectivity are calculated by comparing the retention time and peak area with those of standards (pyrazine and piperazine).

[0056] GC analysis results showed that: Figure 4 The results show that after 2 hours of electrolysis, the piperazine peak appears at 4.911 min, and the peak area exceeds 90%, indicating that pyrazine is largely converted into the hydrogenation product piperazine after 2 hours of hydrogenation reaction, and no by-products are detected. Figure 5 The results showed that after 4 hours of electrolysis, the piperazine peak appeared at 4.911 min, no pyrazine and by-products were detected, the reaction conversion rate reached 100%, and it was highly selective.

[0057] Example 2

[0058] This Example 2 provides a preparation method of a CuCo2O4@NF catalyst and its electrocatalytic hydrogenation performance test for quinoline. This method adjusts the molar ratio of cobalt and copper in the raw materials and adopts a shorter hydrothermal reaction time and a lower calcination system. The specific steps are as follows:

[0059] Example 2 provides a method for preparing a CuCo2O4@NF catalyst, comprising the following steps:

[0060] a) Precursor Solution Preparation: Accurately weigh copper nitrate (Cu(NO₃)₂·3H₂O) (0.04 M), cobalt nitrate (Co(NO₃)₂·6H₂O) (0.09 M, resulting in a Co / Cu molar ratio of 2.25), NH₄F₂ (0.5 M), and urea (0.7 M). Dissolve these solids in 50 mL of deionized water, stirring at medium speed with a magnetic stirrer for 40 minutes until a homogeneous, clear solution is formed.

[0061] b) Hydrothermal Reaction: Transfer the entire precursor solution prepared in step a) to a 100 mL stainless steel autoclave with a Teflon-lined interior. Vertically immerse a 2 cm x 3 cm piece of pretreated nickel foam (NF) in the solution. Ensure the NF does not touch the bottom of the autoclave (a Teflon stand can be used). Seal the autoclave and place it in an oven preheated to 120°C. Maintain this temperature for 6 hours.

[0062] c) Precursor post-treatment: After the reaction is completed, allow the reactor to cool naturally to room temperature in an oven. Carefully open the reactor and remove the nickel foam with the product attached. Use tweezers to pick up the nickel foam and rinse it with a large amount of anhydrous ethanol 3-5 times, then rinse it with a large amount of deionized water 3-5 times, alternating to completely remove residual reactants and unreacted ions on the surface. Place the cleaned nickel foam in a clean Petri dish and dry it in a vacuum drying oven at 70°C for 8 hours to obtain the CuCo2O4@NF precursor.

[0063] d) Calcination: Carefully remove the dried precursor (attached to the nickel foam) from the Petri dish and place it in a clean porcelain boat. Place the boat in the central, constant-temperature zone of a muffle furnace. Close the furnace door and program the temperature from room temperature to 400°C at a rate of 5°C / minute, then hold at 400°C for 3 hours. Calcination is performed in an air atmosphere. After calcination, allow the precursor to cool naturally to room temperature. Remove the boat to obtain the black CuCo2O4@NF catalyst.

[0064] The morphology was characterized by scanning electron microscopy (SEM), and the results showed that uniform spherical nanoneedle structures could still be formed on the three-dimensional skeleton surface of nickel foam despite the adjustment of reaction conditions.

[0065] Example 2 also provides a test of the electrocatalytic hydrogenation performance of a CuCo2O4@NF catalyst for quinoline:

[0066] a) Electrochemical workstation setup and electrolytic cell assembly: A CHI series electrochemical workstation was used. The H-type electrolytic cell was cleaned and dried. The cathode and anode compartments were separated by a Nafion membrane.

[0067] b) Electrode Installation: The prepared CuCo2O4@NF catalyst (effective area calculated based on the actual immersion surface, 1 cm × 1 cm) was installed in the cathode chamber as the working electrode. A platinum sheet (1 cm × 1 cm) was installed in the anode chamber as the counter electrode. A saturated calomel electrode (SCE) was placed in the cathode chamber as the reference electrode, with the salt bridge tip close to the working electrode surface (approximately 2-3 mm).

[0068] c) Electrolyte Preparation and Addition: Prepare 40 mL of a 1.0 M KOH aqueous solution and 40 mL of a 1.0 M KOH aqueous solution containing 0.04 M quinoline. Add the 1.0 M KOH solution containing quinoline to the cathode compartment, and the 1.0 M KOH solution without quinoline to the anode compartment.

[0069] d) Linear Sweep Voltammetry (LSV) or Cyclic Voltammetry (CV) Testing: LSV testing was performed to determine the onset potential and current response of quinoline hydrogenation, and CV testing was performed to evaluate the stability and active sites of the electrode. The scanning parameters were adjusted according to the characteristics of quinoline, as described in Example 1.

[0070] e) Constant-voltage electrolysis: Determine an appropriate hydrogenation potential based on the LSV or CV curve (e.g., approximately -1.25 V vs. SCE, or optimize based on actual test results). Set the electrochemical workstation to constant-voltage electrolysis mode and perform electrolysis. Record the current over time.

[0071] f) Product Sampling and Analysis: After constant-voltage electrolysis has been performed for a certain period of time (e.g., 2 hours, 4 hours, 6 hours, or until the quinoline conversion reaches a plateau), remove a small amount (e.g., 1.0 mL) of the electrolyte sample from the cathode chamber. Because quinoline and its hydrogenation products (e.g., 1,2,3,4-tetrahydroquinoline) may be relatively volatile, quantitative analysis can be performed using high-performance liquid chromatography (HPLC) equipped with a UV detector and a suitable column, such as a C18 column. Alternatively, GC-MS analysis can be performed under appropriate conditions. Quinoline conversion and selectivity for the primary hydrogenation product can be calculated by comparing the retention time and peak area with those of a standard (quinoline and its possible hydrogenation products).

[0072] GC-MS analysis results: Figure 8 The results showed that after 2 h of hydrogenation reaction of CuCo2O4@NF catalyst with quinoline substrate, the tetrahydroquinoline peak appeared at 15.623 min, and the peak area exceeded 50%, indicating that quinoline was largely converted into the hydrogenation product tetrahydroquinoline after 2 h of hydrogenation reaction. The CuCo2O4@NF catalyst can still effectively catalyze the hydrogenation reaction of quinoline and exhibit good catalytic activity and selectivity.

[0073] Example 3

[0074] This Example 3 provides a method for preparing a CuCo2O4@CP catalyst and testing its electrocatalytic hydrogenation performance for pyrazine. The method prepares the catalyst on a carbon paper substrate and uses a relatively low concentration of electrolyte and organic substrate. The specific steps are as follows:

[0075] Example 3 provides a method for preparing a CuCo2O4@CP catalyst, comprising the following steps:

[0076] a) Precursor Solution Preparation: Accurately weigh copper nitrate (Cu(NO₃)₂·3H₂O) (0.06 M), cobalt nitrate (Co(NO₃)₂·6H₂O) (0.12 M, resulting in a Co / Cu molar ratio of 2.0), NH₄F₂ (0.3 M), and urea (0.4 M). Dissolve each of these solids in 50 mL of deionized water, stirring at medium speed with a magnetic stirrer for 30 minutes until a homogeneous, clear solution is formed.

[0077] b) Hydrothermal Reaction: Transfer the entire precursor solution prepared in step a) to a 100 mL stainless steel autoclave lined with Teflon. Vertically immerse a 2 cm x 3 cm piece of pretreated carbon paper (CP) in the solution. Ensure the CP does not touch the bottom of the autoclave (a Teflon stand can be used). Seal the autoclave and place it in an oven preheated to 120°C. Maintain this temperature for 6.5 hours.

[0078] c) Precursor Post-treatment: After the reaction is complete, allow the reactor to cool naturally to room temperature in an oven. Carefully open the reactor and remove the carbon paper with the product attached. Use tweezers to pick up the carbon paper and rinse it with a large amount of anhydrous ethanol 3-5 times, then with a large amount of deionized water 3-5 times, alternating between rinses to completely remove any residual reactants and unreacted ions on the surface. Place the cleaned carbon paper in a clean Petri dish and dry it in a vacuum drying oven at 60°C for 8 hours to obtain the CuCo2O4@CP precursor.

[0079] d) Calcination: Carefully remove the dried precursor (attached to the carbon paper) from the Petri dish and place it in a clean porcelain boat. Place the boat in the central, constant-temperature zone of a muffle furnace. Close the furnace door and program the temperature from room temperature to 420°C at a rate of 5°C / minute, then hold at 420°C for 3.5 hours. Calcination is performed in an air atmosphere. After calcination, allow the mixture to cool naturally to room temperature. Remove the boat to obtain the black CuCo2O4@CP catalyst.

[0080] The morphology was characterized by scanning electron microscopy (SEM), and the results showed that spherical nano-needle-shaped CuCo2O4 structures could be successfully prepared on the surface of carbon paper fibers.

[0081] Example 3 also provides a test of the electrocatalytic hydrogenation performance of a CuCo2O4@CP catalyst for pyrazine:

[0082] a) Electrochemical workstation setup and electrolytic cell assembly: A CHI series electrochemical workstation was used. The H-type electrolytic cell was cleaned and dried. The cathode and anode compartments were separated by a Nafion membrane.

[0083] b) Electrode Installation: Install the prepared CuCo2O4@CP catalyst (effective area calculated based on the actual immersion surface, 1 cm × 1 cm) as the working electrode in the cathode compartment. Install a platinum sheet (1 cm × 1 cm) as the counter electrode in the anode compartment. Place a saturated calomel electrode (SCE) in the cathode compartment as the reference electrode, with the salt bridge tip close to the working electrode surface (approximately 2-3 mm).

[0084] c) Electrolyte Preparation and Addition: Prepare 40 mL of a 0.5 M KOH solution and 40 mL of a 0.5 M KOH solution containing 0.04 M pyrazine. Add the 0.5 M KOH solution containing pyrazine to the cathode compartment, and the 0.5 M KOH solution without pyrazine to the anode compartment.

[0085] d) Electrochemical performance evaluation: Linear sweep voltammetry (LSV) or cyclic voltammetry (CV) tests were performed to evaluate the activity and stability of the catalysts in the presence of low concentrations of electrolyte and low concentrations of organic substrates containing substituents.

[0086] e) Constant-voltage electrolysis: Determine an appropriate hydrogenation potential based on the LSV or CV curve (e.g., approximately -1.15 V vs. SCE, or optimize based on actual test results), and set the electrochemical workstation to constant-voltage electrolysis mode for electrolysis.

[0087] f) Product Sampling and Analysis: After constant-voltage electrolysis at different time points (e.g., 2 hours, 4 hours, and 6 hours), a small amount (e.g., 1.0 mL) of electrolyte sample is taken from the cathode chamber. The sample may require appropriate treatment (e.g., extraction, dilution) before qualitative and quantitative analysis using high-performance liquid chromatography (HPLC, equipped with a UV detector and a suitable chromatographic column, such as a C18 column) or gas chromatography-mass spectrometry (GC-MS) to confirm the conversion of pyrazine and the formation of its hydrogenation product (e.g., piperazine). The conversion rate of pyrazine and the selectivity of the main hydrogenation product are calculated by comparison with the retention time and response of the standard.

[0088] GC-MS analysis results show that the CuCo2O4@CP catalyst can still exhibit electrocatalytic hydrogenation activity for pyrazine even under low KOH concentration electrolyte conditions, demonstrating the adaptability of the catalyst to different electrode substrates and a wide range of electrolyte concentrations.

[0089] Example 4

[0090] This Example 4 provides a preparation method of a CuCo2O4@NF catalyst and its electrocatalytic hydrogenation performance test for pyrazine under conditions where the concentrations of NH4F and urea are greatly adjusted and a high-concentration NaOH electrolyte is used. The specific steps are as follows:

[0091] Example 4 provides a method for preparing a CuCo2O4@NF catalyst, comprising the following steps:

[0092] a) Precursor Solution Preparation: Accurately weigh copper nitrate (Cu(NO₃)₂·3H₂O) (0.04 M), cobalt nitrate (Co(NO₃)₂·6H₂O) (0.08 M, resulting in a Co / Cu molar ratio of 2.0), NH₄F₄ (0.06 M), and urea (0.8 M). Dissolve these solids in 50 mL of deionized water, stirring at medium speed with a magnetic stirrer for 30 minutes until a homogeneous, clear solution is formed.

[0093] b) Hydrothermal Reaction: Transfer the entire precursor solution prepared in step a) to a 100 mL stainless steel autoclave with a Teflon-lined interior. Vertically immerse a 2 cm x 3 cm piece of pretreated nickel foam (NF) in the solution. Ensure the NF does not touch the bottom of the autoclave (a Teflon stand can be used). Seal the autoclave and place it in an oven preheated to 120°C. Maintain this temperature for 7.5 hours.

[0094] c) Precursor post-treatment: After the reaction is completed, allow the reactor to cool naturally to room temperature in an oven. Carefully open the reactor and remove the nickel foam with the product attached. Use tweezers to pick up the nickel foam and rinse it with a large amount of anhydrous ethanol 3-5 times, then rinse it with a large amount of deionized water 3-5 times, alternating to completely remove residual reactants and unreacted ions on the surface. Place the cleaned nickel foam in a clean Petri dish and dry it in a vacuum drying oven at 60°C for 8 hours to obtain the CuCo2O4@NF precursor.

[0095] d) Calcination: Carefully remove the dried precursor (attached to the nickel foam) from the Petri dish and place it in a clean porcelain boat. Place the boat in the central, constant-temperature zone of a muffle furnace. Close the furnace door and program the temperature from room temperature to 480°C at a rate of 5°C / minute, then hold at 480°C for 4.5 hours. Calcination is performed in an air atmosphere. After calcination, allow the mixture to cool naturally to room temperature. Remove the boat to obtain the black CuCo2O4@NF catalyst.

[0096] The morphology was characterized by scanning electron microscopy (SEM), and the results showed that even if the concentration combination of NH4F and urea changed greatly, an effective spherical nanoneedle structure could still be formed on the three-dimensional skeleton surface of nickel foam.

[0097] Example 4 provides a test of the electrocatalytic hydrogenation performance of a CuCo2O4@NF catalyst for pyrazine:

[0098] a) Electrochemical workstation setup and electrolytic cell assembly: A CHI series electrochemical workstation was used. The H-type electrolytic cell was cleaned and dried. The cathode and anode compartments were separated by a Nafion membrane.

[0099] b) Electrode Installation: The prepared CuCo2O4@NF catalyst (effective area calculated based on the actual immersion surface, 1 cm × 1 cm) was installed in the cathode chamber as the working electrode. A platinum sheet (1 cm × 1 cm) was installed in the anode chamber as the counter electrode. A saturated calomel electrode (SCE) was placed in the cathode chamber as the reference electrode, with the salt bridge tip close to the working electrode surface (approximately 2-3 mm).

[0100] c) Electrolyte Preparation and Addition: Prepare 40 mL of 3.0 M NaOH and 40 mL of 3.0 M NaOH containing 0.05 M pyrazine. Add the 3.0 M NaOH solution containing pyrazine to the cathode compartment, and the 3.0 M NaOH solution without pyrazine to the anode compartment.

[0101] d) Electrochemical Performance Evaluation: Linear sweep voltammetry (LSV) or cyclic voltammetry (CV) tests were performed to evaluate the activity and stability of the catalyst under conditions of widely adjusted NH4F and urea concentrations and high NaOH concentration electrolyte.

[0102] e) Constant-voltage electrolysis: Determine an appropriate hydrogenation potential based on the LSV or CV curve (e.g., approximately -1.2 V vs. SCE, or optimize based on actual test results), and set the electrochemical workstation to constant-voltage electrolysis mode for electrolysis.

[0103] f) Product Sampling and Analysis: After constant-voltage electrolysis at various time points (e.g., 2 hours, 4 hours), a small amount (e.g., 0.5 mL) of electrolyte sample is removed from the cathode chamber. After appropriate dilution and filtration, the sample is quantitatively analyzed using a gas chromatograph (GC, equipped with an FID detector and a suitable capillary column). The pyrazine conversion and piperazine selectivity are calculated by comparing the retention time and peak area with those of standards (pyrazine and piperazine).

[0104] GC analysis results show that even under the conditions of low NH4F concentration and high urea concentration in the precursor solution, and high concentration of NaOH in the electrolyte, the prepared CuCo2O4@NF catalyst can still effectively catalyze the conversion of pyrazine to piperazine, showing good catalytic activity and high selectivity, demonstrating the robustness of the preparation method to changes in raw material concentration and the catalyst's tolerance to strong alkaline environments.

[0105] Comparative Example

[0106] Comparative Example 1

[0107] This comparative example 1 aims to simulate the preparation method of a copper cobalt oxide nanowire array electrode disclosed in the prior art CN 116770346 A, and use the catalyst prepared by this method in the pyrazine electrocatalytic hydrogenation reaction of the present invention to evaluate the performance difference.

[0108] Comparative Example 1 provides a method for preparing a CuCo2O4 nanowire array@foam copper catalyst (simulating the prior art CN116770346 A):

[0109] a) Pretreatment of foam copper substrate: Cut commercially available foam copper (different from the foam nickel NF or carbon paper CP used in the embodiments of the present invention, and select foam copper consistent with the prior art) into a size of 2cm×3cm. Immerse it in a 3M HCl aqueous solution and use an ultrasonic cleaner for ultrasonic treatment at room temperature for 15 minutes to remove the surface oxide layer and possible impurities. Take out the foam copper and rinse it repeatedly with a large amount of deionized water until the washing liquid is neutral. Then, immerse the rinsed foam copper in analytical pure acetone and anhydrous ethanol in turn, and ultrasonically clean it for 10 minutes each to remove oil and other organic matter. Finally, rinse it thoroughly again with a large amount of deionized water, and place it in a vacuum drying oven at 60°C to dry for 2 hours for use.

[0110] b) In situ growth of Cu(OH)2 nanowire arrays: The method is carried out in a two-electrode system using a constant current anodic oxidation method. The copper foam sheet pretreated in step a) is used as the anode (working electrode), and a platinum sheet slightly larger than the copper foam (for example, 2.5 cm × 3.5 cm) is selected as the cathode (counter electrode). The two electrodes are placed in parallel in the electrolytic cell, with the inter-electrode distance being about 2 cm. A sufficient amount of 2M KOH aqueous solution is added to the electrolytic cell as an electrolyte to ensure that the copper foam is completely immersed. At room temperature (about 25°C), 20 mA / cm 2 Anodization was carried out at a constant current density (calculated based on the geometric area of ​​the copper foam) for 20 minutes. After the reaction, the copper foam with the blue-green product was carefully removed and the surface was gently rinsed with a large amount of deionized water to remove the residual electrolyte. The copper foam was then dried in an oven at 60°C for 1 hour to obtain Cu(OH)2@copper foam.

[0111] c) Electrochemical deposition of Co(OH)2: This was performed using a three-electrode system using a constant potential deposition method. The Cu(OH)2@copper foam obtained in step b) was used as the working electrode, a platinum sheet was used as the counter electrode, and a saturated calomel electrode (SCE) was connected via a salt bridge as the reference electrode. The electrolyte was a freshly prepared deionized water solution containing 0.05 M Co(NO3)2·6H2O, with no additional pH adjustment. Electrochemical deposition was performed at room temperature using an electrochemical workstation applying a constant potential of -1.0 V (vs. SCE) for 10 minutes. After deposition, the working electrode was carefully removed and the surface was thoroughly rinsed with plenty of deionized water to remove unreacted cobalt salts and residual electrolyte, followed by drying in an oven at 60°C for 1 hour.

[0112] d) Calcination to Conversion into CuCo2O4 Nanowire Arrays: Carefully place the copper foam sample treated and dried in step c) into a clean porcelain boat. Place the boat in the central constant temperature zone of a muffle furnace. Under air, program the temperature from room temperature to 350°C at a rate of 5°C / minute. Hold at 350°C for 2 hours. After calcination, turn off the muffle furnace and allow it to cool naturally to room temperature. Remove the boat to obtain a CuCo2O4 nanowire array-copper foam catalyst with a black product attached.

[0113] The morphology was characterized by scanning electron microscopy (SEM), and the results showed that nanowire or nanorod array structures grew on the surface of the foam copper skeleton, which was significantly different from the spherical nanoneedle morphology formed on the foam nickel or carbon paper in the embodiments of the present invention.

[0114] Comparative Example 1 also provides a CuCo2O4 nanowire array@foam copper catalyst for electrocatalytic hydrogenation of pyrazine:

[0115] a) Electrochemical workstation setup and electrolytic cell assembly: same as step 2.a) in Example 1.

[0116] b) Electrode Installation: Install the CuCo2O4 nanowire array on copper foam catalyst prepared in Step 1 (effective area calculated based on the actual immersion surface, e.g., 1 cm x 1 cm) as the working electrode in the cathode compartment. Install a platinum sheet (1 cm x 1 cm) as the counter electrode in the anode compartment. Place a saturated calomel electrode (SCE) with the salt bridge tip close to the working electrode surface (approximately 2-3 mm) in the cathode compartment as the reference electrode.

[0117] c) Electrolyte preparation and addition: Same as step 2.c) of Example 1, i.e., the cathode compartment contains 40 mL of 1 M KOH aqueous solution containing 0.04 M pyrazine, and the anode compartment contains 40 mL of 1 M KOH aqueous solution.

[0118] d) Linear voltammetry test: Same as step 2.d) of Example 1, scanning was performed in the potential range of 0 V to -1.5 V (vs. SCE) at a rate of 10 mV / s.

[0119] e) Electrochemical activation: As in step 2.e) of Example 1, cyclic voltammetry was performed in the potential range of 1.5 V to -1.5 V (vs. SCE) at a rate of 10 mV / s until the curve stabilized.

[0120] f) Constant-voltage electrolysis: Same as step 2.f) of Example 1, except that a constant potential of -1.167 V (vs. SCE) was applied.

[0121] g) Product sampling and analysis: Similar to step 2.g) of Example 1, after 4 hours of constant voltage electrolysis, a sample was taken from the cathode chamber for GC analysis.

[0122] GC analysis results: After 4 hours of electrolysis, the conversion of pyrazine using the CuCo2O4 nanowire array@copper foam catalyst was lower than that obtained using the CuCo2O4@NF catalyst prepared in Example 1 of the present invention, and the selectivity of piperazine was also lower, accompanied by the formation of more unidentified by-products.

[0123] Conclusion Analysis: While the CuCo2O4 nanowire array on copper foam catalyst prepared by simulating the prior art CN 116770346 A method performs well in the oxygen evolution reaction (OER) from water electrolysis as claimed in the prior art, its catalytic activity and / or selectivity in the pyrazine electrocatalytic hydrogenation reaction of interest to this invention are significantly inferior to the spherical nanoneedle CuCo2O4 catalyst prepared by the present invention via a specific hydrothermal synthesis followed by calcination on a nickel foam or carbon paper substrate. This significant difference in performance highlights the unique and non-obvious nature of the present invention's preparation method (including raw material selection, reaction pathway, substrate type, and resulting microstructure) for achieving efficient electrocatalytic hydrogenation of organic liquids.

[0124] Comparative Example 2

[0125] Comparative Example 2 provides a method for preparing a catalyst (NCF-CuCo2O4@NF) that does not contain NH4F, comprising the following steps:

[0126] a) Precursor Solution Preparation: Accurately weigh Cu(NO₃)₂·3H₂O (0.04 M), Co(NO₃)₂·6H₂O (0.08 M), and urea (0.3 M). Do not add NH₄F. Dissolve each of these solids in 50 mL of deionized water, stirring at medium speed with a magnetic stirrer for 30 minutes until a homogeneous solution is formed.

[0127] b) Hydrothermal reaction: The same as step 1.b) of Example 1, using the above-mentioned precursor solution without NH4F and pretreated nickel foam (NF), at 120°C for 6 hours.

[0128] c) Precursor post-treatment: same as step 1.c) in Example 1.

[0129] d) Calcination: Same as step 1.d) of Example 1, but kept at 400° C. for 3 hours to obtain NCF-CuCo2O4@NF catalyst.

[0130] SEM characterization: The morphology of the obtained product is irregular particles, flaky aggregates or a coating without obvious nanostructure, rather than the clear spherical nanoneedle structure in Example 1.

[0131] Electrocatalytic hydrogenation performance test of NCF-CuCo2O4@NF catalyst for pyrazine:

[0132] The method of steps 2.a) to 2.f) in Example 1 was followed completely. The prepared NCF-CuCo2O4@NF was used as the working electrode. The sample was collected after constant voltage electrolysis at -1.167 V (vs. SCE) for 4 hours.

[0133] GC analysis results: After 4 hours of electrolysis, the conversion rate of pyrazine and / or the selectivity of piperazine were significantly lower than those in Example 1.

[0134] Conclusions and Analysis: NH4F plays a key role in the preparation method of this invention, acting as a morphology modifier or fluorine doping source, promoting the formation of spherical nanoneedle structures with specific high catalytic activity. The absence of NH4F degrades the catalyst's micromorphology, significantly reducing its performance in the electrocatalytic hydrogenation of pyrazine.

[0135] Comparative Example 3

[0136] Comparative Example 3 provides a method for preparing a urea-free catalyst (NU-CuCo2O4@NF), comprising the following steps:

[0137] a) Precursor Solution Preparation: Accurately weigh Cu(NO₃)₂·3H₂O (0.04 M), Co(NO₃)₂·6H₂O (0.08 M), and NH₄F (0.24 M). Do not add urea. Dissolve each of these solids in 50 mL of deionized water, stirring at medium speed with a magnetic stirrer for 30 minutes until a homogeneous solution is formed.

[0138] b) Hydrothermal reaction: The same as step 1.b) of Example 1, using the above-mentioned urea-free precursor solution and pretreated nickel foam (NF), at 120° C. for 6 hours.

[0139] c) Precursor post-treatment: same as step 1.c) in Example 1.

[0140] d) Calcination: Same as step 1.d) of Example 1, but kept at 400° C. for 3 hours to obtain NU-CuCo2O4@NF catalyst.

[0141] SEM characterization: The product is difficult to adhere evenly to the nickel foam, or the formed nanostructure is irregular, such as the nanoneedles are not obvious, are severely agglomerated, or are uneven in size.

[0142] Electrocatalytic hydrogenation performance test of NU-CuCo2O4@NF catalyst for pyrazine:

[0143] The method of steps 2.a) to 2.f) in Example 1 was followed completely. The prepared NU-CuCo2O4@NF was used as the working electrode. The sample was collected after constant voltage electrolysis at -1.167 V (vs. SCE) for 4 hours.

[0144] GC analysis results: After 4 hours of electrolysis, the conversion rate of pyrazine and / or the selectivity of piperazine were significantly lower than those in Example 1.

[0145] Conclusions and Analysis: Urea decomposes under high-temperature hydrothermal conditions to produce NH3 and CO2. The former provides an alkaline environment, promoting the precipitation of hydroxide precursors. Urea also acts as a structure-directing agent or surfactant, affecting crystal growth. The absence of urea alters the morphology and composition of the catalyst, thereby reducing its catalytic performance.

[0146] Comparative Example 4

[0147] Comparative Example 4 provides a method for preparing an uncalcined precursor (P-CuCo2O4@NF), comprising the following steps:

[0148] a) Preparation of precursor solution: same as step 1.a) in Example 1.

[0149] b) Hydrothermal reaction: same as step 1.b) in Example 1.

[0150] c) Precursor post-treatment: Same as step 1.c of Example 1. After this step, the obtained product was directly used for electrochemical testing without calcination.

[0151] SEM characterization: The product is a precursor mixture, which is a hydroxide rather than spinel-structured CuCo2O4. The morphology is different from that after final calcination, and it is not fully formed or has low crystallinity.

[0152] Comparative Example 4 also provides a P-CuCo2O4@NF catalyst for electrocatalytic hydrogenation performance test of pyrazine:

[0153] The method of steps 2.a) to 2.f) in Example 1 was followed. The prepared P-CuCo2O4@NF was used as the working electrode. The sample was collected after 4 hours of constant voltage electrolysis at -1.167 V (vs. SCE).

[0154] GC analysis results: After 4 hours of electrolysis, the conversion rate of pyrazine was extremely low, less than 10%, and almost no obvious catalytic activity was observed.

[0155] Conclusion analysis: The uncalcined precursor has no catalytic activity, and the calcination step is essential for converting the precursor into the CuCo2O4 spinel phase with high catalytic activity.

[0156] Comparative Example 5

[0157] Comparative Example 5 provides a method for preparing a low-temperature calcined catalyst (LT-CuCo2O4@NF), comprising the steps of:

[0158] a) Preparation of precursor solution: same as step 1.a) in Example 1.

[0159] b) Hydrothermal reaction: same as step 1.b) in Example 1.

[0160] c) Precursor post-treatment: same as step 1.c) in Example 1.

[0161] d) Calcination: The dried precursor (attached to nickel foam) was placed in a muffle furnace and heated from room temperature to 250°C at a rate of 5°C / min, then maintained at 250°C for 3 hours. After natural cooling, the LT-CuCo2O4@NF catalyst was obtained.

[0162] SEM characterization and XRD analysis: At 250 °C, the precursor failed to be completely converted into pure CuCo2O4 spinel, and there was an unreacted precursor phase or a spinel phase with low crystallinity.

[0163] Comparative Example 5 also provides a test of the electrocatalytic hydrogenation performance of pyrazine using a LT-CuCo2O4@NF catalyst:

[0164] The method of steps 2.a) to 2.f) in Example 1 was followed completely. The prepared LT-CuCo2O4@NF was used as the working electrode. The sample was collected after constant voltage electrolysis at -1.167 V (vs. SCE) for 4 hours.

[0165] GC analysis results: After 4 hours of electrolysis, the conversion rate of pyrazine and / or the selectivity of piperazine were significantly lower than those in Example 1, and slightly higher than those in Comparative Example 4 which was not calcined.

[0166] Conclusion analysis: Calcination temperature is too low (such as 250℃) which is not enough to completely transform the precursor into the highly active CuCo2O4 spinel phase.

[0167] Comparative Example 6

[0168] Comparative Example 6 provides a method for preparing a high-temperature calcined catalyst (HT-CuCo2O4@NF), comprising the steps of:

[0169] a) Preparation of precursor solution: same as step 1.a) in Example 1.

[0170] b) Hydrothermal reaction: same as step 1.b) in Example 1.

[0171] c) Precursor post-treatment: same as step 1.c) in Example 1.

[0172] d) Calcination: The dried precursor (attached to nickel foam) was placed in a muffle furnace and heated from room temperature to 700°C at a rate of 5°C / min, then held at 700°C for 3 hours. After natural cooling, the HT-CuCo2O4@NF catalyst was obtained.

[0173] SEM characterization: At high temperatures such as 700°C, CuCo2O4 nanostructures (such as nanoneedles) undergo severe sintering and agglomeration, resulting in a significant decrease in specific surface area.

[0174] Comparative Example 6 provides a HT-CuCo2O4@NF catalyst for electrocatalytic hydrogenation performance test of pyrazine:

[0175] The method of steps 2.a) to 2.f) in Example 1 was followed completely. The prepared HT-CuCo2O4@NF was used as the working electrode. The sample was collected after constant voltage electrolysis at -1.167 V (vs. SCE) for 4 hours.

[0176] GC analysis results: After 4 hours of electrolysis, the conversion rate of pyrazine and / or the selectivity of piperazine were significantly lower than those in Example 1 and lower than those in Comparative Example 5 calcined at low temperature.

[0177] Conclusion analysis: Calcination temperature that is too high (such as 700℃) will lead to the destruction of the catalyst nanostructure and the reduction of active sites, thereby seriously damaging its catalytic performance.

[0178] Comparative Example 7

[0179] Comparative Example 7 provides a method for preparing CuCo2O4 powder and a physically supported electrode (Powder-CuCo2O4 / NF), comprising the following steps:

[0180] a) Synthesis of CuCo2O4 powder: The precursor solution prepared in step 1.a) of Example 1 was placed in a 100 mL polytetrafluoroethylene-lined stainless steel autoclave (no substrate was added at this time), sealed, and reacted at 120°C for 6 hours. After the reaction was completed, it was cooled naturally, and the mixture in the autoclave was centrifuged (8000 rpm, 10 minutes) to collect the precipitate. The precipitate was washed alternately with anhydrous ethanol and deionized water 3 times each, and then vacuum-dried at 60°C for 8 hours to obtain a precursor powder. The precursor powder was heated to 400°C at 5°C / min in an air atmosphere in a muffle furnace, kept warm for 3 hours, and ground to obtain CuCo2O4 powder after natural cooling.

[0181] b) Electrode Slurry Preparation and Coating: Weigh 10 mg of the aforementioned CuCo2O4 powder, add 4 mg of conductive carbon black (Vulcan XC-72) and 20 μL of a 5 wt% Nafion solution (as a binder). Then, add approximately 0.5 mL of a 1:1 isopropyl alcohol / water mixture and ultrasonically disperse for 30 minutes to form a uniform catalyst ink.

[0182] c) Electrode preparation: Take a piece of pretreated nickel foam (2 cm × 3 cm) and evenly apply the above catalyst ink to one end (e.g., 1 cm × 1 cm area) using a pipette, controlling the loading to be approximately 1-2 mg / cm 2 (calculated as CuCo2O4) and dried naturally at room temperature, and then dried in vacuum at 60°C for 2 hours to obtain a Powder-CuCo2O4 / NF electrode.

[0183] Comparative Example 7 provides a test of the electrocatalytic hydrogenation performance of a Powder-CuCo2O4 / NF electrode for pyrazine:

[0184] The method of steps 2.a) to 2.f) in Example 1 was followed completely. The prepared Powder-CuCo2O4 / NF was used as the working electrode. The sample was collected after constant voltage electrolysis at -1.167 V (vs. SCE) for 4 hours.

[0185] GC analysis results: After 4 hours of electrolysis, the conversion rate of pyrazine and / or the selectivity of piperazine were inferior to those of the in situ grown CuCo2O4@NF catalyst in Example 1, and the long-term stability of the electrode was poor, and the catalyst was easily detached.

[0186] Conclusion Analysis: In situ growth of the catalyst active material on a conductive substrate (such as nickel foam NF or carbon paper CP) facilitates a closer interface, provides more efficient electron transport channels, and enhances the bonding between the catalyst and the substrate, resulting in superior catalytic activity and stability. This offers significant technical advantages over simply physically mixing and coating pre-synthesized powder catalysts onto a substrate.

[0187] It is obvious to those skilled in the art that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here, and obvious variations or modifications derived therefrom are still within the scope of protection of the claims of the present invention.

Claims

1. Application of a copper-cobalt spinel-based composite catalyst in electrocatalytic hydrogenation of organic liquids.

2. The use according to claim 1, characterized in that The organic liquid is a nitrogen-containing heterocyclic organic compound, and the nitrogen-containing heterocyclic organic compound is at least one compound selected from pyrazine, pyrrole, quinoline and derivatives thereof containing an alkyl group.

3. The use according to any one of claims 1-2, characterized in that The electrolyte for electrocatalytic hydrogenation of organic liquid contains 0.5 mol / L-3.0 mol / L strong alkali aqueous solution and the organic liquid with a concentration of ≤1.5 mol / L.

4. A copper-cobalt spinel-based composite catalyst, characterized in that: The composite catalyst comprises copper-cobalt spinel and is supported on an inert electrode current collector and is used for electrocatalytic hydrogenation of organic liquids.

5. The composite catalyst according to claim 4, characterized in that The inert electrode current collector is selected from one of foamed nickel and carbon paper.

6. The composite catalyst according to claim 4, characterized in that The copper-cobalt spinel is loaded on an inert electrode current collector and presents a spherical nano-needle morphology.

7. A method for preparing a copper-cobalt spinel-based composite catalyst, characterized in that: The following steps are involved: Dissolving a copper source, a cobalt source, NH4F and urea in water to form a precursor solution; Immersing the pretreated inert electrode current collector in the precursor solution and performing a hydrothermal reaction to obtain an inert motor current collector with the precursor attached thereto; The inert motor current collector with the precursor attached thereto is calcined in an air atmosphere to obtain the copper-cobalt spinel-based composite catalyst.

8. The method according to claim 7, characterized in that The temperature of the hydrothermal reaction is 115° C.-120° C., and the reaction time is 6 h-8 h.

9. The method according to claim 7, characterized in that The calcination temperature is 400° C.-500° C., and the calcination time is 3 h-5 h.

10. The method according to claim 7, characterized in that In the precursor solution, the concentration of the copper source is 0.01mol / L-0.1mol / L, the concentration of the cobalt source is 0.0175mol / L-0.225mol / L, the concentration of NH4F is 0.06mol / L-0.6mol / L, and the concentration of urea is 0.08mol / L-0.8mol / L.

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