Application of Pd-Ni-Mo tri-doped mixture electrocatalyst in hydrogenation and dehydrogenation reaction of organic liquid

Abstract

The invention belongs to the technical field of electrochemical electrocatalysis, and particularly relates to application of a Pd-Ni-Mo tri-doped mixture electrocatalyst in organic liquid hydrogenation and dehydrogenation reactions. The invention relates to application of a Pd-Ni-Mo three-doped mixture electrocatalyst in hydrogenation and dehydrogenation reaction of organic liquid. The electrocatalyst is formed by co-depositing palladium, nickel and molybdenum on the surface of an inert electrode material through an electrodeposition method.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical electrocatalysis, and in particular relates to the application of a Pd-Ni-Mo triple-doped mixture electrocatalyst in hydrogenation and dehydrogenation reactions of organic liquids. Background Art

[0002] As a highly promising clean energy source, hydrogen's efficient and safe storage and transportation are key bottlenecks in its large-scale application. Liquid organic hydrogen carrier (LOHC) technology, which stores and releases hydrogen through reversible hydrogenation / dehydrogenation reactions between organic unsaturated compounds and hydrogen, has attracted considerable attention due to its high hydrogen storage density, safe operation, and compatibility with existing fuel distribution infrastructure. However, the practical application of LOHC technology relies heavily on efficient, stable, and economical catalyst systems.

[0003] Currently, noble metal catalysts (especially palladium- and platinum-based catalysts) exhibit excellent catalytic activity and selectivity in the hydrogenation and dehydrogenation reactions of organic liquids. However, the scarcity and high cost of noble metals have greatly restricted their widespread deployment in industrial large-scale LOHC systems, especially in the energy storage field where cost control is strictly required. Therefore, academia and industry have been working hard to reduce the use of noble metals and even develop efficient alternative catalysts that do not contain noble metals at all. Summary of the Invention

[0004] The purpose of the present invention is to solve the above-mentioned shortcomings and provide an application of a Pd-Ni-Mo triple-doped mixture electrocatalyst in the hydrogenation and dehydrogenation reactions of organic liquids.

[0005] The first aspect of the present invention provides an application of a Pd-Ni-Mo triple-doped mixture electrocatalyst in the hydrogenation and dehydrogenation reactions of organic liquids, wherein the electrocatalyst is formed by co-depositing palladium, nickel, and molybdenum on the surface of an inert electrode material by an electrodeposition method.

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

[0007] Furthermore, the electrolyte for the hydrogenation or dehydrogenation reaction 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] The second aspect of the present invention provides a Pd-Ni-Mo triple-doped mixture electrocatalyst, characterized in that the electrocatalyst contains three metal elements: palladium, nickel, and molybdenum, which are co-deposited on the surface of an inert electrode material by an electrodeposition method.

[0009] Furthermore, the inert electrode material is selected from nickel foam (NF) or carbon paper (CP).

[0010] A third aspect of the present invention provides a method for preparing a Pd-Ni-Mo triple-doped mixture electrocatalyst, characterized in that it comprises the following steps:

[0011] preparing an electrolyte containing a palladium source, a nickel source, a molybdenum source and at least one auxiliary material;

[0012] An inert electrode material is used as a working electrode, a saturated calomel electrode is used as a reference electrode, and a platinum sheet is used as a counter electrode. An electrochemical deposition reaction is carried out under certain temperature and constant current conditions, so that palladium, nickel, and molybdenum are co-deposited on the surface of the working electrode to obtain the Pd-Ni-Mo triple-doped mixture electrocatalyst.

[0013] Furthermore, the auxiliary material is selected from at least one of sodium citrate, ammonium chloride, and ammonia water.

[0014] Furthermore, when the auxiliary materials include sodium citrate, ammonium chloride and aqueous ammonia, the concentration of sodium citrate is 40 g / L-50 g / L, the concentration of ammonium chloride is 25 g / L-35 g / L, and the concentration of aqueous ammonia is 65 mL / L-85 mL / L.

[0015] Furthermore, the temperature of the electrochemical deposition reaction is 30°C-50°C, and the cathode current density is -5 mA / cm 2 to -15mA / cm 2 , the reaction time is 2h-6h.

[0016] In a preferred embodiment, in the step of preparing the electrolyte, the concentration of the palladium source is 0.5 g / L-1.5 g / L, the concentration of the nickel source is 40 g / L-60 g / L, and the concentration of the molybdenum source is 10 g / L-20 g / L.

[0017] Beneficial effects of the present invention:

[0018] The Pd-Ni-Mo tri-doped mixture electrocatalyst provided by the present invention and its application in the hydrogenation and dehydrogenation reactions of organic liquids, by adopting an electrodeposition method to directly co-deposit palladium, nickel and molybdenum on the surface of an inert electrode material, the preparation method has a simple process, avoids the complex process and potential activity loss of the traditional multi-step chemical synthesis of catalyst powder and then the electrode preparation, realizes the in-situ growth of the catalyst, greatly simplifies the manufacturing process and reduces energy consumption. The electrodeposition technology can achieve effective regulation of the catalyst components, micromorphology and loading amount, ensures the uniform dispersion and close contact of the three metal elements of palladium, nickel and molybdenum at the atomic or nanoscale, thereby giving full play to its synergistic catalytic effect, and significantly improves the catalytic activity, selectivity and stability of the target organic liquid hydrogenation and dehydrogenation reactions. A strong physical and electrochemical interface is formed between the in-situ generated catalyst layer and the electrode substrate, effectively enhancing the electron transfer efficiency, reducing the interface resistance, and improving the catalyst's anti-stripping ability and long-term operation stability, overcoming the defects of traditional powder catalysts such as easy agglomeration, low utilization of active sites and weak bonding with the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the linear sweep voltammetry test diagram of the hydrogenation reaction of the Pd-Ni-Mo@NF electrode assembled in Example 1.

[0020] Figure 2 This is the cyclic voltammetry curve test diagram of the hydrogenation reaction of the Pd-Ni-Mo@NF electrode assembled in Example 1.

[0021] Figure 3 This is the gas chromatography analysis result after 46 hours of electrochemical hydrogenation of the Pd-Ni-Mo@NF electrode assembled in Example 1.

[0022] Figure 4 This is the linear sweep voltammetry test diagram of the dehydrogenation reaction of the Pd-Ni-Mo@NF electrode assembled in Example 1.

[0023] Figure 5 This is the cyclic voltammetry curve test diagram of the dehydrogenation reaction of the Pd-Ni-Mo@NF electrode assembled in Example 1.

[0024] Figure 6 This is the gas chromatography analysis result after 46 hours of electrochemical dehydrogenation of the Pd-Ni-Mo@NF electrode assembled in Example 1.

[0025] Figure 7 Linear sweep voltammetry test diagram of hydrogenation reaction of Pd-Ni-Mo@CP electrode assembled in Example 2.

[0026] Figure 8 This is the cyclic voltammetry curve test diagram of the hydrogenation reaction of the Pd-Ni-Mo@CP electrode assembled in Example 2.

[0027] Figure 9 This is the gas chromatography analysis result after 48 hours of electrochemical hydrogenation of the Pd-Ni-Mo@CP electrode assembled in Example 2.

[0028] Figure 10 This is the linear sweep voltammetry test diagram of the dehydrogenation reaction of the Pd-Ni-Mo@CP electrode assembled in Example 2.

[0029] Figure 11 This is the cyclic voltammetry curve test diagram of the dehydrogenation reaction of the Pd-Ni-Mo@CP electrode assembled in Example 2.

[0030] Figure 12 This is the gas chromatography analysis result after 48 hours of electrochemical dehydrogenation of the Pd-Ni-Mo@CP electrode assembled in Example 2. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present 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 limiting the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] In the following description, references to "some embodiments" describe a subset of all embodiments, but it is understood that "some embodiments" may be the same subset or different subsets of all embodiments, and may be combined with each other without conflict. Unless otherwise defined, all technical and scientific terms used in the embodiments of the present invention have the same meaning as commonly understood by those skilled in the art to which the embodiments of the present invention pertain. The terms used in the embodiments of the present invention are for the purpose of describing the embodiments of the present invention only and are not intended to limit the present invention.

[0033] Those skilled in the art should understand that in the following description of the embodiments of the present invention, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and 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.

[0034] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "an" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates otherwise.

[0035] It will be understood by those skilled in the art that the numerical ranges in the embodiments of the present invention are to be understood as also specifically disclosing each intermediate value between the upper and lower limits of the ranges. Each smaller range between any stated value and intermediate value in the stated range, as well as any other stated value or intermediate value in the stated range, is also encompassed by the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0036] Unless otherwise indicated, the technical / scientific terms used herein have the same meanings as commonly understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the embodiments or test examples of the present invention. All documents mentioned in this specification are generally incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this application shall prevail.

[0037] It should be noted that all raw materials and / or reagents in the examples of the present invention are purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0038] Raw materials and equipment:

[0039] Palladium source: palladium chloride, analytical grade.

[0040] Nickel source: nickel sulfate, analytical grade.

[0041] Molybdenum source: sodium molybdate, analytical grade.

[0042] Auxiliary materials: sodium citrate, ammonium chloride, ammonia water (25-28%), all of analytical grade.

[0043] Electrode substrate: nickel foam (NF), carbon paper (CP).

[0044] Organic liquid materials: pyrazine, piperazine, pyrrole, pyrrolidine, 2-methylpyrazine, 2-methylpiperazine, all of analytical grade.

[0045] Electrolyte: potassium hydroxide (KOH), sodium hydroxide (NaOH), analytical grade.

[0046] Other reagents: deionized water, acetone, anhydrous ethanol.

[0047] Equipment: electrochemical workstation (such as CHI series), constant temperature magnetic stirring water bath, saturated calomel electrode (SCE), platinum electrode, H-type electrolytic cell, Nafion membrane, gas chromatograph (GC-FID), vacuum drying oven.

[0048] General steps for substrate pretreatment:

[0049] Nickel foam (NF) or carbon paper (CP) substrates were cut into specific sizes (e.g., effective working area 1 cm × 1 cm, actual cut 1 cm × 2 cm, partially immersed in electrolyte). Ultrasonic cleaning was performed in acetone, anhydrous ethanol, and deionized water for 15 minutes each to remove surface oil and impurities. The substrates were then dried in a vacuum oven at 60°C for 2 hours before use.

[0050] Example

[0051] Example 1

[0052] This Example 1 provides a method for preparing an electrocatalyst of a Pd-Ni-Mo triple-doped mixture on a nickel foam substrate (expressed as Pd-Ni-Mo@NF), and tests its electrocatalytic hydrogenation performance for pyrazine and electrocatalytic dehydrogenation performance for piperazine.

[0053] 1. Preparation of Pd-Ni-Mo@NF Electrode

[0054] (a) Raw material preparation and electrolyte preparation:

[0055] Palladium chloride, nickel sulfate, sodium molybdate, sodium citrate, and ammonium chloride are added to a beaker in sequence, and about 40mL deionized water is added and stirred at room temperature using a magnetic stirrer until completely dissolved. Then concentrated ammonia is slowly added dropwise, and stirring is continued. Finally, the solution is transferred to a 50mL volumetric flask, fixed to the mark with deionized water, shaken up, and a uniform and transparent electrolyte is obtained. In this electrolyte, palladium chloride concentration is about 1.0g / L, nickel sulfate concentration is about 50g / L, sodium molybdate concentration is about 15g / L, sodium citrate concentration is about 45g / L, ammonium chloride concentration is about 30.4g / L, and concentrated ammonia concentration is about 75mL / L.

[0056] (b) Electrochemical deposition:

[0057] Assemble a three-electrode electrolytic cell: use a pretreated nickel foam sheet as the working electrode (the effective geometric area immersed in the electrolyte is set to 1.0 cm × 1.0 cm, and the rest is wrapped with insulating tape or the immersion depth is controlled by a clamp), select a large area (5 cm × 5 cm) platinum sheet as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode through a Luggin capillary.

[0058] Pour 50 mL of the electrolyte prepared in step (a) into the electrolytic cell, and place the entire electrolytic cell in a constant temperature magnetic stirring water bath at 40° C., and turn on magnetic stirring to keep the solution uniform.

[0059] Connect the electrochemical workstation. Set the constant current deposition mode and apply a cathode current of -10.0 mA (corresponding to a current density of -10.0 mA / cm2 over the geometric area of ​​the working electrode). 2The electrochemical deposition reaction was initiated and lasted for 3.0 hours. After the deposition was complete, the power was turned off and the working electrode (i.e., the Pd-Ni-Mo@NF electrode) was carefully removed. Immediately, the electrode surface was thoroughly rinsed with a large amount of deionized water to remove any residual electrolyte and loosely attached materials. Finally, the cleaned Pd-Ni-Mo@NF electrode was dried in a vacuum drying oven at 60°C for 2 hours and stored for later use.

[0060] 2. Pd-Ni-Mo@NF electrocatalytic pyrazine hydrogenation performance test

[0061] (a) Electrolysis system and electrolyte configuration:

[0062] An H-type glass electrolytic cell with a Nafion 117 proton exchange membrane separating the cathode and anode compartments was used.

[0063] Cathode chamber (working electrode chamber): add 40.0 mL of electrolyte consisting of 1.0 M KOH aqueous solution and 0.04 M pyrazine (strong base concentration 1.0 M, organic liquid pyrazine concentration 0.04 M).

[0064] Anode chamber (counter electrode chamber): Add 40.0 mL of 1.0 M KOH aqueous solution.

[0065] (b) Electrode installation and electrochemical test setup:

[0066] The prepared Pd-Ni-Mo@NF electrode was installed as the cathode (working electrode).

[0067] A platinum sheet (1.0 cm x 1.0 cm) was installed as an anode (counter electrode).

[0068] The tip of the Luggin capillary of a saturated calomel electrode (SCE) was placed close to the surface of the working electrode (about 2-3 mm) as a reference electrode in the cathode chamber.

[0069] Connect the electrochemical workstation. First, perform electrochemical activation: Scan the electrolytic cell in the range of 0-1.5V (vs. SCE) at a rate of 0.01V / s. The linear sweep voltammetry test results are as follows: Figure 1 As shown by Figure 1 It can be seen that in the voltage range below -1.1V, 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. In the potential range of 0V to -1.5V (vs. SCE), cyclic voltammetry (CV) scans were performed at a scan rate of 10mV / s for several cycles until the CV curve was basically stable. The cyclic voltammetry curve test results are shown in Figure 2. Figure 2 shown.

[0070] After activation, the electrochemical reaction was carried out in a constant potential electrolysis mode, with a constant potential of -1.167 V (vs. SCE) applied for electrocatalytic hydrogenation of pyrazine. The total electrolysis time was 46 hours.

[0071] (c) Product sampling and analysis:

[0072] After 46 hours of electrolysis, a small amount (eg, 0.5 mL) of electrolyte sample was carefully taken out from the cathode chamber.

[0073] Sample pretreatment: As needed, the sample can be diluted a certain multiple with an appropriate amount of solvent (such as methanol or a solvent containing an internal standard) and filtered through a 0.22 μm filter membrane to remove solid particles.

[0074] Gas chromatography (GC-FID) analysis: The pretreated sample is injected into a gas chromatograph (equipped with an FID detector and a suitable capillary column, such as HP-5). By comparing the retention time and peak area with those of pre-calibrated pyrazine (raw material) and piperazine (main product) standards, the remaining amount of pyrazine in the reaction solution and the amount of piperazine produced are quantitatively analyzed. The results are as follows: Figure 3 As shown by Figure 3 It can be seen that after 46 hours of hydrogenation, a piperazine peak appeared at 7.793 minutes, and the calculated conversion rate was 52.35% and the selectivity was 85.0%.

[0075] 3. Pd-Ni-Mo@NF electrocatalytic piperazine dehydrogenation performance test

[0076] (a) Electrolysis system and electrolyte configuration:

[0077] The same H-type electrolytic cell as used in the hydrogenation test was used.

[0078] Anode chamber (working electrode chamber): add 40.0 mL of electrolyte consisting of 1.0 M KOH aqueous solution and 0.04 M piperazine (strong base concentration 1.0 M, organic liquid piperazine concentration 0.04 M).

[0079] Cathode chamber (counter electrode chamber): Add 40.0 mL of 1.0 M KOH aqueous solution.

[0080] (b) Electrode installation and electrochemical test setup:

[0081] The prepared Pd-Ni-Mo@NF electrode was installed as the anode (working electrode).

[0082] A platinum sheet (1.0 cm x 1.0 cm) was installed as a cathode (counter electrode).

[0083] The tip of the Luggin capillary of a saturated calomel electrode (SCE) was placed close to the surface of the working electrode and placed in the anode chamber.

[0084] Connect the electrochemical workstation. First, perform electrochemical activation: Scan the electrolytic cell in the range of -0.155-0.745V (vs. SCE) at a rate of 0.01V / s. The linear sweep voltammetry test results are as follows: Figure 4 As shown by Figure 4 It can be seen that in the range of 0.4-0.7V, the experimental group with piperazine added has a higher current density than the blank control group without piperazine, indicating that the dehydrogenation reaction is dominant in this range. Cyclic voltammetry (CV) scans were performed for several cycles at a scan rate of 10mV / s in the potential range of -0.155V to 0.745V (vs. SCE) until the CV curve was basically stable. The cyclic voltammetry curve test results are shown in Figure 2. Figure 5 shown.

[0085] After activation, a constant potential electrolysis mode was set, and a constant potential of 0.478 V (vs. SCE) was applied to carry out the electrocatalytic dehydrogenation reaction of piperazine. The total electrolysis time was 46 hours.

[0086] (c) Product sampling and analysis:

[0087] After 46 hours of electrolysis, a small amount (eg, 0.5 mL) of electrolyte sample was taken from the anode chamber.

[0088] The sample pretreatment and GC-FID analysis methods are the same as those for the above-mentioned pyrazine hydrogenation product analysis, but this time the focus is on the consumption of piperazine and the formation of pyrazine. The results are as follows: Figure 6 As shown by Figure 6 It can be seen that after 46 hours of dehydrogenation, pyrazine appeared at 5.941 minutes, no piperazine and by-products were detected, the reaction conversion rate reached 100%, and it was highly selective.

[0089] Example 2

[0090] This Example 2 provides a method for preparing an electrocatalyst of a Pd-Ni-Mo triple-doped mixture on a carbon paper substrate (expressed as Pd-Ni-Mo@CP).

[0091] 1. Preparation of Pd-Ni-Mo@CP Electrode

[0092] (a) Raw material preparation and electrolyte preparation:

[0093] Palladium chloride, nickel sulfate, sodium molybdate, sodium citrate, and ammonium chloride are added to a beaker in sequence, and about 40 mL of deionized water is added and stirred at room temperature using a magnetic stirrer until completely dissolved. Then concentrated ammonia is slowly added dropwise and stirring is continued. Finally, the solution is transferred to a 50 mL volumetric flask, fixed to the mark with deionized water, and shaken. In this electrolyte, the concentration of palladium chloride is 0.5 g / L, the concentration of nickel sulfate is 40 g / L, the concentration of sodium molybdate is 10 g / L, the concentration of sodium citrate is set to 40 g / L, the concentration of ammonium chloride is 25 g / L, and the concentration of concentrated ammonia is 65 mL / L.

[0094] (b) Electrochemical deposition:

[0095] Assemble a three-electrode electrolytic cell: use the pretreated carbon paper (CP) as the working electrode (the effective geometric area is set to 1.0 cm×1.0 cm), and the rest is the same as in Example 1.

[0096] Pour 50 mL of the electrolyte prepared in step (a) into the electrolytic cell, and place the entire electrolytic cell in a constant temperature magnetic stirring water bath at 30° C., and turn on magnetic stirring.

[0097] Connect the electrochemical workstation. Set the constant current deposition mode and apply a cathode current of -5.0 mA (corresponding to a current density of -5.0 mA / cm 2 The electrochemical deposition reaction was started and lasted for 2.0 hours. The subsequent treatment was the same as in Example 1.

[0098] 2. Pd-Ni-Mo@CP electrocatalytic pyrazine hydrogenation performance test

[0099] (a) Electrolysis system and electrolyte configuration:

[0100] Same as Example 1.

[0101] (b) Electrode installation and electrochemical test setup:

[0102] The same process as in Example 1 was used, except that the working electrode was the Pd-Ni-Mo@CP prepared in this example. The activation steps and the potentiostatic electrolysis potential (-1.167 V vs. SCE) and time (46 hours) remained the same as in Example 1.

[0103] (c) Product sampling and analysis:

[0104] The analysis method is the same as in Example 1.

[0105] Analysis results: Figure 9 As shown in the figure, after 48 h of hydrogenation, a piperazine peak appeared at 7.793 min, and the Pd-Ni-Mo@CP electrode had a high conversion rate for the hydrogenation reaction of pyrazine.

[0106] 3. Pd-Ni-Mo@CP electrocatalytic piperazine dehydrogenation performance test

[0107] (a) Electrolysis system and electrolyte configuration:

[0108] Same as Example 1.

[0109] (b) Electrode installation and electrochemical test setup:

[0110] The same process as in Example 1 was used, except that the working electrode was the Pd-Ni-Mo@CP prepared in this example. The activation steps and the potentiostatic electrolysis potential (0.478 V vs. SCE) and time (46 hours) remained the same as in Example 1.

[0111] (c) Product sampling and analysis:

[0112] The analysis method is the same as in Example 1.

[0113] Analysis results: Figure 12 As shown, the activity of the Pd-Ni-Mo@CP electrode for the dehydrogenation reaction of piperazine is lower than that in Example 1, but it still has a certain activity.

[0114] Example 3

[0115] This Example 3 studies the effect of electrochemical deposition time on the performance of Pd-Ni-Mo@NF electrode.

[0116] 1. Preparation of Pd-Ni-Mo@NF Electrode

[0117] (a) Raw material preparation and electrolyte preparation:

[0118] Same as Example 1.

[0119] (b) Electrochemical deposition:

[0120] Except that the electrochemical deposition time was set to 4.0 hours, all other conditions (including substrate, temperature 40 °C, current density -10.0 mA / cm 2 etc.) are the same as in Example 1.

[0121] 2. Pd-Ni-Mo@NF electrocatalytic pyrazine hydrogenation performance test

[0122] (a) Electrolysis system and electrolyte configuration: same as in Example 1.

[0123] (b) Electrode installation and electrochemical test setup: same as in Example 1.

[0124] (c) Product sampling and analysis: The analysis method is the same as in Example 1.

[0125] Analysis results: Properly increasing the deposition time will lead to an increase in the catalyst loading, but has no significant effect on the catalytic performance. The conversion rate and selectivity of the pyrazine hydrogenation reaction are similar to those of Example 1.

[0126] 3. Pd-Ni-Mo@NF electrocatalytic piperazine dehydrogenation performance test

[0127] (a) Electrolysis system and electrolyte configuration: same as in Example 1.

[0128] (b) Electrode installation and electrochemical test setup: same as in Example 1.

[0129] (c) Product sampling and analysis: The analysis method is the same as in Example 1.

[0130] Analysis results: The conversion rate and selectivity of the piperazine dehydrogenation reaction are similar to those of Example 1.

[0131] Example 4

[0132] This Example 4 studies the effect of electrochemical deposition temperature on the performance of Pd-Ni-Mo@NF electrodes.

[0133] 1. Preparation of Pd-Ni-Mo@NF Electrode

[0134] (a) Raw material preparation and electrolyte preparation:

[0135] Same as Example 1.

[0136] (b) Electrochemical deposition:

[0137] Except that the electrochemical deposition temperature was set to 35°C, all other conditions (including substrate, current density -10.0 mA / cm 2 , time 3.0 hours, etc.) are the same as in Example 1.

[0138] 2. Pd-Ni-Mo@NF Electrocatalytic Pyrazine Hydrogenation Performance Test (Comparative Example 1)

[0139] (a) Electrolysis system and electrolyte configuration: same as in Example 1.

[0140] (b) Electrode installation and electrochemical test setup: same as in Example 1.

[0141] (c) Product sampling and analysis: The analysis method is the same as in Example 1.

[0142] Analysis results: Slightly lowering the deposition temperature has a slight effect on the morphology or crystallinity of the catalyst, and the catalytic performance fluctuates slightly, but the conversion rate and selectivity of the pyrazine hydrogenation reaction are still similar to the results of Example 1.

[0143] 3. Pd-Ni-Mo@NF electrocatalytic piperazine dehydrogenation performance test

[0144] (a) Electrolysis system and electrolyte configuration: same as in Example 1.

[0145] (b) Electrode installation and electrochemical test setup: same as in Example 1.

[0146] (c) Product sampling and analysis: The analysis method is the same as in Example 1.

[0147] Analysis results: The conversion rate and selectivity of the piperazine dehydrogenation reaction are similar to those of Example 1.

[0148] Example 5

[0149] This Example 5 studies the effect of changes in the concentration of sodium citrate in the auxiliary material on the performance of the Pd-Ni-Mo@NF electrode.

[0150] 1. Preparation of Pd-Ni-Mo@NF Electrode

[0151] (a) Raw material preparation and electrolyte preparation:

[0152] Except that the concentration of sodium citrate was set to 40 g / L, the concentrations of all other raw materials (palladium chloride 1.0 g / L, nickel sulfate 50 g / L, sodium molybdate 15 g / L, ammonium chloride 30.4 g / L, concentrated ammonia 75 mL / L) were the same as those in Example 1.

[0153] (b) Electrochemical deposition:

[0154] All conditions (substrate, temperature 40°C, current density -10.0 mA / cm 2 , time 3.0 hours, etc.) are the same as in Example 1.

[0155] 2. Pd-Ni-Mo@NF electrocatalytic pyrazine hydrogenation performance test

[0156] (a) Electrolysis system and electrolyte configuration: same as in Example 1.

[0157] (b) Electrode installation and electrochemical test setup: same as in Example 1.

[0158] (c) Product sampling and analysis: The analysis method is the same as in Example 1.

[0159] Analysis results: Sodium citrate is used as a complexing agent. Although the concentration change slightly affects the deposition rate of metal ions and the microstructure of the resulting catalyst, the overall performance remains good. The conversion rate and selectivity of the pyrazine hydrogenation reaction are still similar to those of Example 1.

[0160] 3. Pd-Ni-Mo@NF electrocatalytic piperazine dehydrogenation performance test

[0161] (a) Electrolysis system and electrolyte configuration: same as in Example 1.

[0162] (b) Electrode installation and electrochemical test setup: same as in Example 1.

[0163] (c) Product sampling and analysis: The analysis method is the same as in Example 1.

[0164] Analysis results: The conversion rate and selectivity of the piperazine dehydrogenation reaction are similar to those of Example 1.

[0165] Comparative Example

[0166] Comparative Example 1

[0167] Comparative Example 1 (using the preparation method of the prior art CN 105990588 A and performing the performance test of this application)

[0168] Comparative Example 1 describes a method for preparing a bifunctional Pd / Ni-Mo / C composite catalyst disclosed in Chinese Patent No. 105990588 A. This catalyst is primarily used for oxygen reduction and oxygen evolution reactions. In this comparative example, the catalyst electrode prepared using this method was used in the pyrazine electrocatalytic hydrogenation and piperazine electrocatalytic dehydrogenation performance tests described in Example 1 of this application to evaluate its performance compared to the in-situ electrodeposition method proposed in this application.

[0169] 1. Preparation of Pd / Ni-Mo / C catalyst powder

[0170] (a) Preparation of Ni-Mo / C carrier (refer to prior art CN 105990588 A and Example 1 steps 1) and 2)):

[0171] Appropriate amounts of nickel nitrate and ammonium molybdate are accurately weighed as Ni and Mo sources, respectively, to achieve a Ni to Mo mass ratio of 4:1 (refer to the ratio of Ni:Mo=4:1 in Example 1 of the prior art). The metal salts are dissolved in an appropriate amount of ethanol aqueous solution.

[0172] A certain mass of BP1000 carbon powder (as the conductive carbon support C) was weighed and added to the above metal salt solution to ensure that the total mass of Ni and Mo metals accounted for 20% of the total mass of Ni-Mo / C.

[0173] The mixture was dispersed uniformly by ultrasonication in a water bath at 65°C, and then evaporated to dryness with stirring. The obtained solid was dried in vacuo at 60-80°C and ground for later use.

[0174] The ground powder was placed in a porcelain boat and placed in a tubular heating furnace. A mixed atmosphere (e.g., a flow ratio of 9:5, see prior art Example 1) is introduced. After the airflow stabilizes, the temperature is raised at a constant rate to 500°C and reduced at this temperature for 2 hours. After the reaction is completed, the temperature is lowered to room temperature under the protective atmosphere, and Ni-Mo / C powder is obtained.

[0175] (b) Pd is loaded on Ni-Mo / C (refer to the prior art and step 3 of Example 1):

[0176] 60 mg of the Ni-Mo / C powder prepared above was weighed and added to 20 mL of ethylene glycol, and ultrasonically dispersed for 30 minutes to form a uniform suspension.

[0177] 3 mg of PVP (polyvinylpyrrolidone, as a stabilizer, refer to prior art example 1) was added to the suspension.

[0178] An appropriate amount of palladium chloride (PdCl) was weighed and dissolved in a small amount of ethylene glycol, and then slowly added dropwise to the above-mentioned Ni-Mo / C suspension so that the mass of the Pd element accounted for 10% of the total mass of the final Pd / Ni-Mo / C catalyst (refer to the Pd loading in Example 1 of the prior art).

[0179] The mixed solution was magnetically stirred at room temperature for 2 hours, then heated in an oil bath to 140°C and refluxed at this temperature for 3 hours.

[0180] After the reaction is complete, the mixture is cooled to room temperature. The solid product is collected by filtration and washed several times with anhydrous ethanol. The resulting Pd / Ni-Mo / C catalyst powder is dried overnight in a vacuum oven at 70°C and ground for later use.

[0181] (c) Preparation of Pd / Ni-Mo / C / NF electrode:

[0182] Accurately weigh 10.0 mg of the prepared Pd / Ni-Mo / C catalyst powder and add 2.0 mg of conductive carbon black (e.g., Super P). Then, add 50 μL of a 5 wt% Nafion solution and approximately 0.5 mL of a 1:1 isopropanol / water mixed solvent. Ultrasonic dispersion is performed for 30 minutes to form a catalyst ink.

[0183] Take a piece of pre-treated nickel foam (NF, effective geometric area 1.0 cm×1.0 cm) and evenly drop the catalyst ink on its surface to control the loading amount.

[0184] After air-drying at room temperature, the mixture was dried in an oven at 60°C for 2 h to obtain a Pd / Ni-Mo / C / NF electrode.

[0185] 2. Pd / Ni-Mo / C / NF electrocatalytic pyrazine hydrogenation performance test (same conditions as Example 1 of the present application)

[0186] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 2 (a) of Example 1 of the present application.

[0187] (b) Electrode Installation and Electrochemical Test Setup: The Pd / Ni-Mo / C / NF electrode prepared in this comparative example was installed as the cathode. The rest was the same as Part 2(b) of Example 1 of this application.

[0188] (c) Product sampling and analysis: The analysis method is exactly the same as that in Part 2 (c) of Example 1 of the present application.

[0189] Analysis results: The pyrazine conversion rate is significantly lower than that of the Pd-Ni-Mo@NF electrode prepared by in-situ electrodeposition in Example 1 of the present application.

[0190] 3. Pd / Ni-Mo / C / NF electrocatalytic piperazine dehydrogenation performance test (same conditions as Example 1 of the present application)

[0191] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 3 (a) of Example 1 of the present application.

[0192] (b) Electrode Installation and Electrochemical Test Setup: The Pd / Ni-Mo / C / NF electrode prepared in this comparative example was installed as the anode. The rest of the steps were the same as those in Part 3(b) of Example 1 of this application.

[0193] (c) Product sampling and analysis: The analysis method is exactly the same as that in Part 3 (c) of Example 1 of the present application.

[0194] Analysis results: The piperazine conversion rate is expected to be significantly lower than that in Example 1 of the present application.

[0195] Comparative Example 2

[0196] This comparative example 2 aims to prepare a Pd-Ni bimetallic catalyst that does not contain molybdenum, and compare its performance with that of the Pd-Ni-Mo trimetallic catalyst in Example 1.

[0197] 1. Preparation of Pd-Ni@NF Electrode

[0198] (a) Raw material preparation and electrolyte preparation:

[0199] Accurately weigh 0.050g palladium chloride, 2.500g nickel sulfate, 2.250g sodium citrate, and 1.520g ammonium chloride, and add 3.75mL concentrated ammonia. Do not add any molybdenum source. Dissolve in 50mL deionized water and bring to volume. The concentrations of the remaining electrolyte components are consistent with those in Example 1.

[0200] (b) Electrochemical deposition:

[0201] All conditions (substrate NF, temperature 40°C, current density -10.0 mA / cm 2 , time 3.0 hours, etc.) are exactly the same as those in Part 1 (b) of Example 1.

[0202] 2. Pd-Ni@NF electrocatalytic pyrazine hydrogenation performance test

[0203] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 2 (a) of Example 1.

[0204] (b) Electrode installation and electrochemical test setup: The Pd-Ni@NF electrode prepared in this comparative example was used as the working electrode, and the rest was the same as in Part 2 (b) of Example 1.

[0205] (c) Product sampling and analysis: The analysis method is the same as that in part 2 (c) of Example 1.

[0206] Analysis results show that without the synergistic effect of molybdenum, the hydrogenation activity and / or piperazine selectivity of the Pd-Ni@NF catalyst for pyrazine are significantly lower than those of the Pd-Ni-Mo@NF catalyst in Example 1. Pyrazine conversion drops to 25-35%, and piperazine selectivity drops to 60-70%. This demonstrates that the addition of molybdenum is crucial for improving the overall performance of the catalyst, and the synergistic effect of a ternary metal cannot be simply matched by a binary metal.

[0207] 3. Pd-Ni@NF electrocatalytic piperazine dehydrogenation performance test

[0208] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 3 (a) of Example 1.

[0209] (b) Electrode installation and electrochemical test setup: The Pd-Ni@NF electrode prepared in this comparative example was used as the working electrode, and the rest was the same as Part 3 (b) of Example 1.

[0210] (c) Product sampling and analysis: The analysis method is the same as that in Part 3 (c) of Example 1.

[0211] Analysis results: Similarly, the performance (conversion and selectivity) of Pd-Ni@NF in the piperazine dehydrogenation reaction will also be significantly inferior to that of Pd-Ni-Mo@NF in Example 1.

[0212] Comparative Example 3

[0213] This comparative example 3 aims to prepare a Ni-Mo bimetallic catalyst that does not contain precious metal palladium, and compares its performance with that of Example 1.

[0214] 1. Preparation of Ni-Mo@NF Electrode

[0215] (a) Raw material preparation and electrolyte preparation:

[0216] Accurately weigh 2.500g nickel sulfate, 0.750g sodium molybdate, 2.250g sodium citrate, and 1.520g ammonium chloride, and add 3.75mL of concentrated aqueous ammonia. Do not add any palladium source. Dissolve in 50mL of deionized water and bring to volume. The concentrations of the remaining electrolyte components are consistent with those in Example 1.

[0217] (b) Electrochemical deposition:

[0218] All conditions (substrate NF, temperature 40°C, current density -10.0 mA / cm 2 , time 3.0 hours, etc.) are exactly the same as those in Part 1 (b) of Example 1.

[0219] 2. Performance test of Ni-Mo@NF electrocatalytic pyrazine hydrogenation

[0220] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 2 (a) of Example 1.

[0221] (b) Electrode installation and electrochemical test setup: The Ni-Mo@NF electrode prepared in this comparative example was used as the working electrode, and the rest was the same as that in part 2 (b) of Example 1.

[0222] (c) Product sampling and analysis: The analysis method is the same as that in part 2 (c) of Example 1.

[0223] Analysis results showed that due to the lack of the highly active precious metal palladium, the Ni-Mo@NF catalyst showed little activity in the hydrogenation of pyrazine, or the conversion rate was extremely low (less than 5%), making it ineffective in catalyzing the reaction. This fully demonstrates the key role of palladium as a catalytic active center.

[0224] 3. Performance test of Ni-Mo@NF electrocatalytic piperazine dehydrogenation

[0225] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 3 (a) of Example 1.

[0226] (b) Electrode installation and electrochemical test setup: The Ni-Mo@NF electrode prepared in this comparative example was used as the working electrode, and the rest was the same as Part 3 (b) of Example 1.

[0227] (c) Product sampling and analysis: The analysis method is the same as that in Part 3 (c) of Example 1.

[0228] Analysis results: Similarly, Ni-Mo@NF will also exhibit extremely low catalytic activity in the piperazine dehydrogenation reaction.

[0229] Comparative Example 4

[0230] This comparative example 4 is intended to study the effect of too low an electrochemical deposition temperature on the performance of the Pd-Ni-Mo@NF electrode, and to compare it with Example 1.

[0231] 1. Preparation of Pd-Ni-Mo@NF Electrode

[0232] (a) Raw material preparation and electrolyte preparation:

[0233] Completely the same as Part 1 (a) of Example 1.

[0234] (b) Electrochemical deposition:

[0235] The three-electrode electrolytic cell and the working electrode, counter electrode, and reference electrode were assembled in the same manner as in Example 1.

[0236] Pour 50 mL of the electrolyte prepared in step (a) into the electrolytic cell, and place the entire electrolytic cell in a constant temperature magnetic stirring water bath at 10° C., and turn on magnetic stirring.

[0237] Connect the electrochemical workstation. Set the constant current deposition mode and apply a cathode current of -10.0 mA (current density -10.0 mA / cm 2 ), the duration is 3.0 hours (the same as in Example 1). The subsequent treatment is the same as in Example 1.

[0238] 2. Pd-Ni-Mo@NF (low temperature deposition) electrocatalytic pyrazine hydrogenation performance test

[0239] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 2 (a) of Example 1.

[0240] (b) Electrode installation and electrochemical test setup: Same as part 2(b) of Example 1.

[0241] (c) Product sampling and analysis: The analysis method is the same as that in part 2 (c) of Example 1.

[0242] Analysis results showed that due to the low deposition temperature, the diffusion and deposition kinetics of the metal ions were severely inhibited, resulting in an uneven catalyst layer, poor adhesion, low crystallinity, and an imbalanced metal ratio. Consequently, the pyrazine conversion rate was significantly lower than in Example 1, below 20%, and the piperazine selectivity was also poor.

[0243] 3. Pd-Ni-Mo@NF (low temperature deposition) electrocatalytic piperazine dehydrogenation performance test

[0244] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 3 (a) of Example 1.

[0245] (b) Electrode installation and electrochemical test setup: Same as part 3(b) of Example 1.

[0246] (c) Product sampling and analysis: The analysis method is the same as that in Part 3 (c) of Example 1.

[0247] Analysis results: Similarly, due to defects in the catalyst structure and composition, the piperazine dehydrogenation performance will be significantly inferior to that of Example 1.

[0248] Comparative Example 5

[0249] This comparative example 5 is intended to study the effect of excessively high cathode current density on the performance of the Pd-Ni-Mo@NF electrode, and to compare it with Example 1.

[0250] 1. Preparation of Pd-Ni-Mo@NF Electrode

[0251] (a) Raw material preparation and electrolyte preparation:

[0252] Completely the same as Part 1 (a) of Example 1.

[0253] (b) Electrochemical deposition:

[0254] The three-electrode electrolytic cell and the electrode arrangement were assembled as in Example 1. The electrolytic cell was placed in a constant temperature magnetic stirring water bath at 40°C.

[0255] Connect the electrochemical workstation. Set the constant current deposition mode and apply a cathode current of -30.0 mA (corresponding to a current density of -30.0 mA / cm 2 ), the duration is 1.0 hour. The subsequent treatment is the same as in Example 1.

[0256] 2. Pd-Ni-Mo@NF (high current density deposition) electrocatalytic pyrazine hydrogenation performance test

[0257] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 2 (a) of Example 1.

[0258] (b) Electrode installation and electrochemical test setup: Same as part 2(b) of Example 1.

[0259] (c) Product sampling and analysis: The analysis method is the same as that in part 2 (c) of Example 1.

[0260] Analysis results show that excessively high current density results in a loose, dendritic deposit with poor adhesion, accompanied by severe hydrogen evolution side reactions, which impair effective metal deposition and alloy formation. Consequently, pyrazine conversion is significantly lower than in Example 1, for example, below 25%, and selectivity is also affected.

[0261] 3. Pd-Ni-Mo@NF (high current density deposition) electrocatalytic piperazine dehydrogenation performance test

[0262] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 3 (a) of Example 1.

[0263] (b) Electrode installation and electrochemical test setup: Same as part 3(b) of Example 1.

[0264] (c) Product sampling and analysis: The analysis method is the same as that in Part 3 (c) of Example 1.

[0265] Analysis results: Due to the inferior structure of the catalyst, the piperazine dehydrogenation performance will also be significantly worse than that of Example 1.

[0266] Comparative Example 6

[0267] This comparative example 6 aims to study the effect on the performance of the Pd-Ni-Mo@NF electrode when one of the key auxiliary materials (such as sodium citrate, which usually acts as a complexing agent to affect the deposition potential and morphology of metal ions) is missing from the electrolyte, and compares it with Example 1.

[0268] 1. Preparation of Pd-Ni-Mo@NF Electrode

[0269] (a) Raw material preparation and electrolyte preparation:

[0270] Except for not adding sodium citrate, all other raw materials (palladium chloride, nickel sulfate, sodium molybdate, ammonium chloride, concentrated ammonia solution) and their concentrations are the same as those in Part 1 (a) of Example 1.

[0271] (b) Electrochemical deposition:

[0272] All conditions (substrate, temperature 40°C, current density -10.0 mA / cm 2 , time 3.0 hours, etc.) are the same as those in Part 1 (b) of Example 1.

[0273] 2. Performance test of electrocatalytic pyrazine hydrogenation over Pd-Ni-Mo@NF (lacking sodium citrate)

[0274] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 2 (a) of Example 1.

[0275] (b) Electrode installation and electrochemical test setup: Same as part 2(b) of Example 1.

[0276] (c) Product sampling and analysis: The analysis method is the same as that in part 2 (c) of Example 1.

[0277] Analysis results: Sodium citrate, as a complexing agent, helps regulate the metal ion deposition process and promotes the formation of a uniform, dense catalyst layer. The absence of sodium citrate leads to direct and rapid metal ion deposition, resulting in an uneven, rough surface and even significant variations in the deposition potentials of different metals, making it difficult to form an ideal alloy or a closely contacting multimetallic structure. Consequently, the pyrazine conversion was significantly lower than in Example 1, and selectivity also decreased.

[0278] 3. Performance test of electrocatalytic piperazine dehydrogenation over Pd-Ni-Mo@NF (lacking sodium citrate)

[0279] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 3 (a) of Example 1.

[0280] (b) Electrode installation and electrochemical test setup: Same as part 3(b) of Example 1.

[0281] (c) Product sampling and analysis: The analysis method is the same as that in Part 3 (c) of Example 1.

[0282] Analysis results: Due to the decrease in catalyst quality, the piperazine dehydrogenation performance is significantly inferior to that of Example 1.

[0283] Comparative Example 7

[0284] This comparative example 7 is intended to study the effect of excessively high organic liquid (substrate) concentration in the electrolyte on the catalytic performance (especially hydrogenation) of the Pd-Ni-Mo@NF electrode, and is compared with Example 1 and Example 3 (organic liquid concentration 1.5 mol / L).

[0285] 1. Preparation of Pd-Ni-Mo@NF Electrode

[0286] Completely the same as Part 1 of Example 1.

[0287] 2. Pd-Ni-Mo@NF electrocatalytic pyrazine hydrogenation performance test (high substrate concentration)

[0288] (a) Electrolysis system and electrolyte configuration:

[0289] The cathode chamber: 40.0 mL of electrolyte solution consisting of 1.0 M KOH aqueous solution and 3.0 M pyrazine (the concentration of organic liquid pyrazine is 3.0 M) was added. The anode chamber was the same as in Example 1.

[0290] (b) Electrode installation and electrochemical test setup: Same as part 2(b) of Example 1.

[0291] (c) Product sampling and analysis: The analysis method is the same as that in part 2 (c) of Example 1.

[0292] Analysis results show that excessively high substrate concentrations can lead to: 1) increased competition for substrate adsorption on the electrode surface, hindering the generation or adsorption of H*; 2) increased solution viscosity, limiting mass transfer; and 3) accelerated catalyst poisoning or deactivation. Consequently, despite high substrate concentrations, the conversion per unit time does not increase proportionally; in fact, the conversion rate is significantly lower than that achieved at the upper limit of the claimed substrate concentration (e.g., 1.5 M in Example 3), and selectivity also decreases.

[0293] 3. Pd-Ni-Mo@NF electrocatalytic piperazine dehydrogenation performance test (high substrate concentration)

[0294] This comparative example focuses on the effect of high substrate concentration in hydrogenation reactions. High substrate concentration in dehydrogenation reactions also brings similar mass transfer and adsorption issues, but the influencing mechanisms are slightly different. They can be briefly described or omitted here to highlight the comparison of hydrogenation.

[0295] Analysis results: The piperazine dehydrogenation performance is not as good as that within the concentration range specified in the claims due to mass transfer limitations or electrode passivation caused by high concentrations.

[0296] Comparative Example 8

[0297] This comparative example 8 aims to study the effect of too short an electrochemical deposition time on the performance of the Pd-Ni-Mo@NF electrode and compare it with Example 1.

[0298] 1. Preparation of Pd-Ni-Mo@NF electrode (short deposition time)

[0299] (a) Preparation of raw materials and electrolyte: exactly the same as in Part 1 (a) of Example 1.

[0300] (b) Electrochemical deposition: Except that the electrochemical deposition time was set to 0.5 h, all other conditions (substrate NF, temperature 40° C., current density −10.0 mA / cm 2 , etc.) were the same as in Example 1.

[0301] 2. Pd-Ni-Mo@NF (short-time deposition) electrocatalytic pyrazine hydrogenation performance test

[0302] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 2 (a) of Example 1.

[0303] (b) Electrode installation and electrochemical test setup: Same as part 2(b) of Example 1.

[0304] (c) Product sampling and analysis: The analysis method is the same as that in part 2 (c) of Example 1.

[0305] Analysis results: The deposition time was too short, resulting in a severely insufficient catalyst loading. The resulting catalyst layer was very thin or even discontinuous, with very few active sites. Consequently, the pyrazine conversion rate was very low.

[0306] 3. Pd-Ni-Mo@NF (short-time deposition) electrocatalytic piperazine dehydrogenation performance test

[0307] (a) Electrolysis system and electrolyte configuration: exactly the same as Part 3 (a) of Example 1.

[0308] (b) Electrode installation and electrochemical test setup: Same as part 3(b) of Example 1.

[0309] (c) Product sampling and analysis: The analysis method is the same as that in Part 3 (c) of Example 1.

[0310] Analysis results: The dehydrogenation performance was also extremely poor due to insufficient catalyst loading.

[0311] Comparative Example 9

[0312] Comparative Example 9 aims to study the effect of too low a concentration of a strong alkali aqueous solution in the electrolyte on the catalytic performance of the Pd-Ni-Mo@NF electrode, and compare it with Example 1.

[0313] 1. Preparation of Pd-Ni-Mo@NF Electrode

[0314] Completely the same as Part 1 of Example 1.

[0315] 2. Pd-Ni-Mo@NF electrocatalytic pyrazine hydrogenation performance test (low base concentration)

[0316] (a) Electrolysis system and electrolyte configuration:

[0317] The cathode chamber: 40.0 mL of electrolyte solution consisting of 0.05 M KOH aqueous solution and 0.04 M pyrazine (strong base concentration 0.05 M, far below the lower limit of 0.5 M required by the claim) was added. The anode chamber: 40.0 mL of 0.05 M KOH aqueous solution was added.

[0318] (b) Electrode installation and electrochemical test setup: Same as part 2(b) of Example 1.

[0319] (c) Product sampling and analysis: The analysis method is the same as that in part 2 (c) of Example 1.

[0320] Analysis Results: An alkaline environment is crucial for many hydrogenation / dehydrogenation reactions (especially those involving proton transfer in aqueous systems) and also affects electrode stability and ionic conductivity. Excessively low base concentrations lead to slow reaction kinetics, hindered proton donation / acceptance, and decreased electrolyte conductivity. Consequently, pyrazine conversion was significantly lower than in Example 1.

[0321] 3. Pd-Ni-Mo@NF electrocatalytic piperazine dehydrogenation performance test (low base concentration)

[0322] (a) Electrolysis system and electrolyte configuration:

[0323] To the anode chamber: add 40.0 mL of an electrolyte consisting of a 0.05 M KOH aqueous solution and 0.04 M piperazine. To the cathode chamber: add 40.0 mL of a 0.05 M KOH aqueous solution.

[0324] (b) Electrode installation and electrochemical test setup: Same as part 3(b) of Example 1.

[0325] (c) Product sampling and analysis: The analysis method is the same as that in Part 3 (c) of Example 1.

[0326] Analysis results: The dehydrogenation performance also decreased significantly due to the low alkali concentration.

[0327] 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 modifications or substitutions that can be easily conceived by a person 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 based on the scope of protection of the claims.

Claims

1. Application of a Pd-Ni-Mo triple-doped mixture electrocatalyst in hydrogenation and dehydrogenation reactions of organic liquids, characterized in that: The electrocatalyst is formed by co-depositing palladium, nickel and molybdenum on the surface of an inert electrode material through an electrodeposition method.

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

3. The use according to claim 1 or 2, characterized in that The electrolyte for the hydrogenation or dehydrogenation reaction 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.

4. A Pd-Ni-Mo triple-doped mixture electrocatalyst, characterized in that: The electrocatalyst comprises three metal elements, palladium, nickel and molybdenum, which are co-deposited on the surface of the inert electrode material by an electrodeposition method.

5. The electrocatalyst according to claim 4, characterized in that The inert electrode material is selected from nickel foam (NF) or carbon paper (CP).

6. A method for preparing a Pd-Ni-Mo triple-doped mixture electrocatalyst, characterized in that: The following steps are involved: preparing an electrolyte containing a palladium source, a nickel source, a molybdenum source and at least one auxiliary material; An inert electrode material is used as a working electrode, a saturated calomel electrode is used as a reference electrode, and a platinum sheet is used as a counter electrode. An electrochemical deposition reaction is carried out under certain temperature and constant current conditions, so that palladium, nickel, and molybdenum are co-deposited on the surface of the working electrode to obtain the Pd-Ni-Mo triple-doped mixture electrocatalyst.

7. The method according to claim 6, characterized in that The auxiliary material is selected from at least one of sodium citrate, ammonium chloride and ammonia water.

8. The method according to claim 7, characterized in that When the auxiliary materials include sodium citrate, ammonium chloride and aqueous ammonia, the concentration of sodium citrate is 40g / L-50g / L, the concentration of ammonium chloride is 25g / L-35g / L, and the concentration of aqueous ammonia is 65mL / L-85mL / L.

9. The method according to claim 6, characterized in that The temperature of the electrochemical deposition reaction is 30°C-50°C, and the cathode current density is -5 mA / cm 2 to -15mA / cm 2 , the reaction time is 2h-6h.

10. The method according to claim 6, characterized in that The concentration of the palladium source in the electrolyte in step (a) is 0.5 g / L-1.5 g / L, the concentration of the nickel source is 40 g / L-60 g / L, and the concentration of the molybdenum source is 10 g / L to 20 g / L.

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