A non-metal modified nickel-cobalt catalyst, a preparation method and application thereof

Abstract

The present application relates to a kind of non-metal modified nickel-cobalt catalyst and its preparation method and application, belong to liquid organic hydrogen carrier electrochemical hydrogen storage catalyst technical field.The present application provides a kind of preparation method of non-metal modified nickel-cobalt catalyst, CoNi / NF catalyst is modified with non-metal, the non-metal includes phosphorus or fluorine;When the non-metal is phosphorus, CoNi / NF catalyst is mixed with phosphorus source, in inert gas atmosphere, heat treatment obtains CoNiP / NF catalyst;When the non-metal is fluorine, in-situ electrodeposition is carried out with foam nickel as substrate, the electrolyte used for in-situ electrodeposition contains cobalt ion, nickel ion and fluorine ion, obtains CoNiF / NF catalyst.The present application is used as working electrode, catalyzes quinoxaline hydrogenation reaction or tetrahydroquinoxaline dehydrogenation reaction, further improves the conversion rate and selectivity of reaction, inhibits the occurrence of side reaction, and the electrochemical stability is strong, improves its long-term service performance as electrode.

Description

Technical Field

[0001] This invention relates to the field of catalysts for electrochemical hydrogen storage on liquid organic hydrogen carriers, and particularly to a non-metallic modified nickel-cobalt catalyst, its preparation method, and its application. Background Technology

[0002] The reversible hydrogenation-dehydrogenation reaction of aromatic nitrogen heterocyclic compounds such as quinoline and quinoxaline with their hydrogenated derivatives is the core reaction system for the reversible hydrogen storage-desorption of liquid organic hydrogen carriers. Currently, the mainstream catalytic systems in the industry are divided into two main categories: noble metal catalysts and ordinary transition metal-based catalysts.

[0003] Noble metal (Pt, Pd) catalysts exhibit high activity in hydrogenation and dehydrogenation, but are extremely expensive, scarce, and prone to particle agglomeration and loss of active sites during electrochemical cycling, resulting in poor stability and hindering large-scale application. Conventional non-noble metal (pure Ni, pure Co) catalysts are inexpensive, but their bifunctional compatibility is extremely poor, making them unsuitable for both hydrogenation-reduction and dehydrogenation bidirectional reactions. Conventional non-metallic doped catalysts suffer from disordered doping, single active sites, and the tendency to form inert oxide layers on their surfaces, making it difficult to simultaneously achieve high conversion rates and selectivity for both hydrogenation and dehydrogenation reactions, and they are prone to deactivation over long periods. Therefore, existing non-noble metal catalysts cannot meet the requirements for bifunctional catalysis of directed hydrogenation and dehydrogenation of nitrogen heterocyclic compounds, and suffer from technical problems such as low activity, poor selectivity, and uncontrollable doping.

[0004] CoNi / NF catalysts are supported bimetallic catalysts, typically using a cobalt-nickel alloy (CoNi) as the active component and nickel foam (NF) as the conductive support. The core of this catalyst lies in enhancing catalytic performance through the synergistic effect of cobalt and nickel, and the three-dimensional porous structure of nickel foam. Current mainstream methods for preparing CoNi / NF electrodes include hydrothermal methods, sol-gel coating methods, powder bonding coating methods, and non-in-situ deposition methods. Hydrothermal methods suffer from stringent conditions, poor controllability of material growth, and a tendency to agglomerate and collapse; powder coating methods require the addition of binders and other insulating agents, resulting in high interfacial impedance, masking of active sites, and easy detachment of active materials; non-in-situ deposition methods suffer from weak substrate adhesion and poor uniformity of the deposited layer. Traditional processes generally exhibit poor repeatability, large batch-to-batch variations, and insufficient electrode cycling stability, making it difficult to simultaneously meet the demands of high electrode performance and large-scale production. In addition, when conventional CoNiF / NF catalysts are used as electrodes, phenomena such as shedding of catalytic active components and deterioration of surface structure are prone to occur during repeated hydrogenation and dehydrogenation reactions, leading to electrode performance degradation and decreased cycle stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a non-metallic modified nickel-cobalt catalyst, its preparation method, and its application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing a non-metal-modified nickel-cobalt catalyst, wherein a CoNi / NF catalyst is modified with a non-metal, the non-metal including phosphorus or fluorine; In-situ electrodeposition was performed using nickel foam as a substrate. The electrolyte used for in-situ electrodeposition contained cobalt ions and nickel ions to obtain a CoNi / NF catalyst. When the non-metal is phosphorus, the CoNi / NF catalyst is mixed with a phosphorus source and heat-treated at 250~350℃ for 2~4 h in an inert gas atmosphere to obtain the CoNiP / NF catalyst. When the non-metal is fluorine, in-situ electrodeposition is performed using nickel foam as a substrate. The electrolyte used for in-situ electrodeposition contains cobalt ions, nickel ions, and fluorine ions to obtain the CoNiF / NF catalyst.

[0007] This invention introduces non-metallic elements (phosphorus or fluorine) into conventional CoNiF / NF catalysts, enhancing the structural integrity of the CoNi catalyst layer, improving the catalyst's mechanical strength, chemical stability, and interfacial degradation resistance, inhibiting the dissolution and aggregation of active components during catalysis, mitigating excessive adsorption of intermediates, reducing the damage to the electrode caused by side reactions such as HER / OER, and improving the long-term operational stability of the electrode. Specifically, phosphorus modification offers advantages in constructing a stable active phase and enhancing the structural strength of the catalyst layer, improving electrode stability, and inhibiting structural damage and electrochemical performance degradation during electrocatalytic operation. Fluorine modification offers advantages in improving adsorption behavior, enhancing selectivity, slowing down degradation, and inhibiting mechanical shedding, suppressing bubble-induced mechanical degradation, and mitigating Faraday efficiency loss caused by competing side reactions. In addition, compared with CoNiP / NF catalysts, CoNiF / NF catalysts have the following advantages: (1) Fluorine has a higher electronegativity than phosphorus, which can regulate the electron cloud distribution of the active metal centers of Co and Ni, improve the adsorption and activation ability of the electrode for the C=N unsaturated bonds in quinoxaline and tetrahydroquinoxaline molecules, and improve the substrate conversion efficiency; (2) Fluorine ions have a smaller radius, and after doping, they can build abundant lattice defects on the catalyst surface, increase the number of effective active sites, accelerate the dissociation of electrolyte to generate active hydrogen atoms, reduce the overpotential of hydrogenation reaction, and optimize reaction kinetics; (3) CoNiF / NF catalysts can efficiently catalyze quinoxaline under the same potential window. Hydrogenation can efficiently catalyze the dehydrogenation of tetrahydroquinoxaline, resulting in better conversion and selectivity, making it suitable for systems requiring reversible reactions, such as flow batteries; (4) The surface of the CoNiF / NF catalyst can form a protective interface, inhibiting the dissolution of active metals in alkaline electrolytes, electrode corrosion, and carbon poisoning in organic intermediate volumes. At the same time, the surface is hydrophobic, effectively extending the electrode cycle life; (5) The electrode charge transfer impedance is lower, the Tafel slope is smaller, and the reaction kinetics are better. Under the same working conditions, the Faraday efficiency and energy efficiency are higher than those of the CoNiP / NF catalyst; (6) The CoNiF / NF preparation process is mild, safe, low-consumption, and easy to industrialize. It does not require high-temperature reaction, has no high-temperature thermal damage, low production energy consumption, and releases no phosphorus-containing waste liquid or toxic gases, resulting in high batch stability.

[0008] Meanwhile, this invention uses in-situ electrodeposition to achieve direct growth of active materials on the surface of NF substrate, resulting in strong adhesion and resistance to detachment; no binder is required, reducing interfacial impedance and effectively improving electrochemical activity and reaction efficiency; the process conditions are mild and the cycle is short, the composition and loading are controllable, the finished product has good consistency and is suitable for mass production; the microstructure is uniform and porous, effectively increasing the number of active sites, and the electrode has excellent long-cycle stability.

[0009] Furthermore, the concentration of the cobalt ions is preferably 0.1~0.3 M, for example, including but not limited to any point value or any range of two points from 0.1 M, 0.12 M, 0.15 M, 0.18 M, 0.2 M, 0.22 M, 0.25 M, 0.28 M and 0.3 M; And / or, the concentration of nickel ions is preferably 0.1 to 0.3 M, for example, including but not limited to any point value or any range of two points from 0.1 M, 0.12 M, 0.15 M, 0.18 M, 0.2 M, 0.22 M, 0.25 M, 0.28 M and 0.3 M; And / or, the concentration of the fluoride ions is preferably 0.05 to 0.1 M, for example, including but not limited to any point value or any range of two points from 0.05 M, 0.06 M, 0.07 M, 0.08 M, 0.09 M and 0.1 M.

[0010] Furthermore, the cobalt ions may be derived from cobalt chloride hexahydrate, the nickel ions may be derived from nickel chloride hexahydrate, and the fluoride ions may be derived from ammonium fluoride.

[0011] Furthermore, the voltage for in-situ electrodeposition is preferably -1.1 to -1.3 V vs. SCE, including, but not limited to, any point value or a range of any two points among -1.1 V vs. SCE, -1.2 V vs. SCE, -1.4 V vs. SCE, -1.6 V vs. SCE, -1.8 V vs. SCE, -1.2 V vs. SCE, -1.22 V vs. SCE, -1.24 V vs. SCE, -1.26 V vs. SCE, -1.28 V vs. SCE, and -1.3 V vs. SCE. And / or, the in-situ electrodeposition time is preferably 1 to 3 hours, for example, including but not limited to any point value or any range of any two points from 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours and 3 hours.

[0012] Furthermore, the in-situ electrodeposition temperature is preferably 35~45℃, for example, including but not limited to any point value or any range of two points among 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, 41℃, 42℃, 43℃, 44℃ and 45℃.

[0013] Furthermore, magnetic stirring is performed during in-situ electrodeposition. The magnetic stirring speed is preferably 400~600 r / min, for example, including but not limited to any point value or any range of two points from 400 r / min, 450 r / min, 500 r / min, 550 r / min and 600 r / min.

[0014] Furthermore, the electrolyte also contains choline chloride and propylene glycol as solvents. Traditional electrodeposition electrolytes use water as a solvent, which is prone to drawbacks such as severe hydrogen evolution side reactions, uneven metal ion deposition rates, easy agglomeration and detachment of nanosheets, and poor adhesion to the electrode substrate, thus reducing electrode cycle stability and rate performance. This invention uses a eutectic solvent system (DES) of choline chloride and propylene glycol as the solvent. This system relies on stable hydrogen bonding between choline chloride and propylene glycol to form a homogeneous, green solvent system with low viscosity, high stability, and a wide electrochemical window at room temperature. Simultaneously, this system can uniformly dissociate and disperse cobalt and nickel metal precursor ions, effectively controlling the reduction rate and diffusion behavior of metal ions, providing a crucial environment for the in-situ growth of uniform, ordered, and stable CoNi nanosheet array structures, thereby ensuring the microstructure and electrochemical performance of the catalyst.

[0015] Compared with electrolytes using water as a solvent, this invention uses choline chloride and propylene glycol as solvents, which has the following advantages: (1) Suppressing side reactions and improving deposition purity. The DES system has no free water molecules, eliminating hydrogen evolution side reactions during electrodeposition, avoiding pinholes, cracks, and loose defects on the electrode surface, and the prepared CoNi / NF coating is dense, uniform, and has significantly improved crystal integrity. (2) Regulating ion deposition kinetics. The hydrogen bond network of the DES system can moderately bind cobalt and nickel metal ions, reduce the ion reduction rate, realize cobalt-nickel bimetallic co-deposition, induce orderly growth of two-dimensional nanosheet arrays, avoid nanostructure stacking and agglomeration, and increase the electrode active specific surface area and the number of active sites. (3) Strengthening interfacial bonding strength. The DES system can optimize the wettability of the substrate surface, promote the direct in-situ bonding and growth of active materials such as Co and Ni on the current collector surface, reduce interfacial gaps and detachment risks, and improve structural stability and cycle life. (4) Broadening the process window. The DES system is less affected by fluctuations in temperature and current density, has strong deposition process stability, and can prepare catalysts with uniform performance in batches, reducing the problem of large batch differences.

[0016] Compared with other DES systems using choline chloride and propylene glycol as solvents, the present invention uses choline chloride and propylene glycol as solvents, which has the following advantages: (1) Compared with the choline chloride-urea DES system: the choline chloride-urea DES system is prone to decomposition at high temperature to produce ammonia gas, which can easily cause impurities on the electrode surface and generate pore defects. Moreover, the conductivity of the system fluctuates greatly and the deposition uniformity is poor. The DES system of the present invention has no easily decomposable components, no impurities are generated throughout the process, the electrode purity is high, the structure is complete, and the electrochemical impedance is lower. (2) Compared with the choline chloride-ethylene glycol DES system: ethylene glycol has high toxicity and poor biocompatibility. Moreover, the electrochemical window of the system is narrow. Under high current deposition, solvent decomposition is easy to occur, which limits the improvement of electrode performance. The propylene glycol used in the present invention is low in toxicity and safe, with a wider electrochemical window, which can be adapted to a wide range of deposition potentials and has stronger process adaptability. (3) Compared with the DES system of choline chloride-glycerol: The DES system of choline chloride-glycerol has extremely high viscosity, large ion mass transfer resistance, slow metal ion diffusion, and is prone to uneven deposition layer thickness and blockage of active sites, which affects the rate performance of the electrode; The DES system of this invention has moderate viscosity, high ion conduction efficiency, and excellent mass transfer kinetics, which can quickly generate ultrathin, ordered, and permeable nanosheet array structure, improve electrolyte penetration and ion migration efficiency, and have higher electrode rate performance and energy storage performance.

[0017] Furthermore, the molar ratio of choline chloride to propylene glycol is preferably choline chloride:propylene glycol = 1:(1~3), for example, including but not limited to any point value or any range value composed of any two points such as 1:1, 1:1.5, 1:2, 1:2.5 and 1:3.

[0018] Furthermore, the electrolyte also contains citric acid, which acts as a complexing agent and can complex Ni. 2+ Metal ions such as Mo slow down the metal deposition rate, resulting in a uniform and delicate coating, preventing the agglomeration and clumping of nanoparticles, stabilizing the electrolyte pH, preventing the precipitation of metal hydroxides, and improving the catalytic morphology of the electrode.

[0019] Furthermore, the concentration of the citric acid is preferably 0.6 to 0.8 M, for example, including but not limited to any point value or any range of two points from 0.6 M, 0.62 M, 0.64 M, 0.66 M, 0.68 M, 0.7 M, 0.72 M, 0.74 M, 0.76 M, 0.78 M, 0.8 M.

[0020] Furthermore, the choline chloride is mixed with propylene glycol, and after it is completely dissolved and a deep eutectic solvent is formed, cobalt chloride hexahydrate, nickel chloride hexahydrate and citric acid are added. The mixture is then magnetically stirred until all components are dissolved to obtain the electrolyte used for in-situ electrodeposition.

[0021] Furthermore, the mixing temperature of choline chloride and propylene glycol is preferably 40-50°C, for example, including but not limited to any point value or any range of two points from 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C and 50°C.

[0022] Furthermore, the magnetic stirring temperature is preferably 40~50℃, for example, including but not limited to any point value or any two points within the range of 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃ and 50℃; the magnetic stirring speed is preferably 400~600 r / min, for example, including but not limited to any point value or any two points within the range of 400 r / min, 450 r / min, 500 r / min, 550 r / min and 600 r / min; the magnetic stirring time is preferably 10~16 h, for example, including but not limited to any point value or any two points within the range of 10 h, 11 h, 12 h, 13 h, 14 h, 15 h and 16 h.

[0023] Furthermore, the phosphorus source includes sodium hypophosphite, and the ratio of the CoNi / NF catalyst to sodium hypophosphite is CoNi / NF catalyst: sodium hypophosphite = 1 cm⁻¹. 2 : (400~800) mg is appropriate, for example, including but not limited to = 1 cm 2 400 mg, 1 cm 2 500 mg, 1 cm 2 600 mg, 1 cm 2 700 mg and 1 cm 2 : any point value in 800 mg, etc., or a range of values ​​consisting of any two points.

[0024] Furthermore, the inert gas includes at least one of nitrogen, argon, and helium.

[0025] Furthermore, when the non-metal is phosphorus, the heat treatment temperature is preferably 250~350℃, for example, including but not limited to any point value or any two points of 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃ and 350℃; the heat treatment time is preferably 2~4 h, for example, including but not limited to any point value or any two points of 2 h, 2.5 h, 3 h, 3.5 h and 4 h.

[0026] Furthermore, when the non-metal is phosphorus, the heat treatment heating rate is preferably 3~6℃ / min, for example, including but not limited to any point value or any range of two points from 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min, 5℃ / min, 5.5℃ / min and 6℃ / min.

[0027] Furthermore, the CoNiP / NF catalyst was electrochemically activated using cyclic voltammetry to obtain an electrochemically activated CoNiP / NF catalyst.

[0028] Furthermore, electrolysis was performed using platinum as the counter electrode and CoNiP / NF catalyst as the working electrode, with potassium hydroxide in the electrolyte.

[0029] Furthermore, the concentration of potassium hydroxide is preferably 0.5 to 2 M, for example, including but not limited to any point value or any range of two points from 0.5 M, 0.8 M, 1 M, 1.5 M, 1.8 M and 2 M.

[0030] Furthermore, the test potential range is set from open circuit potential to -0.45 V vs. RHE, and the scan rate is preferably 5~150 mV / s, such as but not limited to 5 mV / s, 10 mV / s, 15 mV / s, 20 mV / s, 25 mV / s, 30 mV / s, 35 mV / s, 40 mV / s, 45 mV / s, 50 mV / s, 55 mV / s, 60 mV / s, 65 mV / s, 70 mV / s, 75 mV / s, 80 mV / s, 85 mV / s, 90 mV / s, 95 mV / s, 100 mV / s, 105 mV / s, 110 mV / s, 115 mV / s, 120 mV / s, 125 mV / s, 130 mV / s, 135 mV / s, 140 mV / s, etc. Any point value or a range of any two points from mV / s, 145 mV / s, and 150 mV / s; the cumulative number of cyclic scans should preferably be 40 to 60, for example, including but not limited to any point value or a range of any two points from 40, 45, 50, 55, and 60.

[0031] Secondly, the present invention provides a non-metallic modified nickel-cobalt catalyst, which is prepared by the preparation method described above.

[0032] Thirdly, the present invention provides the application of the non-metallic modified nickel-cobalt catalyst in the catalytic hydrogenation reaction of quinoxaline or the dehydrogenation reaction of tetrahydroquinoxaline.

[0033] Fourthly, the present invention provides a method for catalytic hydrogenation of quinoxaline, wherein the non-metallic modified cobalt nickel catalyst is used as the working electrode, platinum is used as the counter electrode, and mercury / mercury oxide is used as the reference electrode, and electrolysis is performed. The electrolyte for catalytic hydrogenation of quinoxaline contains water, potassium hydroxide and quinoxaline.

[0034] Furthermore, the electrolysis temperature is preferably 35~45℃, for example, including but not limited to any point value or any range of two points among 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, 41℃, 42℃, 43℃, 44℃ and 45℃.

[0035] Furthermore, the electrolytic constant potential is preferably -0.45 to -0.25 V vs. RHE, for example including but not limited to -0.45 V vs. RHE, -0.44 V vs. RHE, -0.43 V vs. RHE, -0.42 V vs. RHE, -0.41 V vs. RHE, -0.4 V vs. RHE, -0.39 V vs. RHE, -0.38 V vs. RHE, -0.37 V vs. RHE, -0.36 V vs. RHE, -0.35 V vs. RHE, -0.34 V vs. RHE, -0.33 V vs. RHE, -0.32 V vs. RHE, -0.31 V vs. RHE, -0.3 V vs. RHE, -0.29 V vs. RHE, -0.28 V vs. RHE, -0.27 V vs. RHE, and -0.26 V. The range of values ​​between or between any two points, such as vs. RHE and -0.25 V vs. RHE.

[0036] Furthermore, magnetic stirring is performed during electrolysis, with a stirring speed preferably between 400 and 600 r / min, including but not limited to any point value or any range of two points from 400 r / min, 450 r / min, 500 r / min, 550 r / min and 600 r / min.

[0037] Furthermore, the working electrode and the reference electrode are placed in the cathode cavity of the electrolytic cell, the counter electrode is placed in the anode cavity, and an anion exchange membrane is placed between the cathode cavity and the anode cavity.

[0038] Furthermore, the concentration of potassium hydroxide is preferably 0.5~2 M, for example, including but not limited to any point value or any range of two points from 0.5 M, 0.8 M, 1 M, 1.5 M, 1.8 M and 2 M.

[0039] Furthermore, the concentration of the quinoxaline is preferably 10-20 mM, for example, including but not limited to any point value or any range of two points such as 10 mM, 12 mM, 15 mM, 18 mM and 20 mM.

[0040] Furthermore, the electrolyte for catalytic hydrogenation of quinoxaline may also contain dioxane, wherein the concentration of dioxane is preferably 8 vol% to 12 vol%, for example, including but not limited to any point value or any two points of 8 vol%, 9 vol%, 10 vol%, 11 vol%, and 12 vol%.

[0041] Fifthly, the present invention provides a method for catalyzing the dehydrogenation reaction of tetrahydroquinoxaline, wherein the non-metallic modified cobalt nickel catalyst is used as the working electrode, platinum is used as the counter electrode, and mercury / mercury oxide is used as the reference electrode, and electrolysis is performed. The electrolyte for catalyzing the dehydrogenation of tetrahydroquinoxaline contains water, potassium hydroxide and tetrahydroquinoxaline.

[0042] Furthermore, the electrolysis temperature is preferably 35~40℃, for example, including but not limited to any point value or any range of two points among 35℃, 36℃, 37℃, 38℃, 39℃ and 40℃.

[0043] Furthermore, the electrolytic constant potential is preferably 1.45~1.55 V vs. RHE, such as, but not limited to, any point value or a range of any two points from 1.45V vs. RHE, 1.46V vs. RHE, 1.47V vs. RHE, 1.48V vs. RHE, 1.49V vs. RHE, 1.5V vs. RHE, 1.51V vs. RHE, 1.52V vs. RHE, 1.53V vs. RHE, 1.54V vs. RHE, and 1.55V vs. RHE.

[0044] Furthermore, magnetic stirring is performed during electrolysis, with a stirring speed preferably between 400 and 600 r / min, including but not limited to any point value or any range of two points from 400 r / min, 450 r / min, 500 r / min, 550 r / min and 600 r / min.

[0045] Furthermore, the working electrode and the reference electrode are placed in the cathode cavity of the electrolytic cell, the counter electrode is placed in the anode cavity, and an anion exchange membrane is placed between the cathode cavity and the anode cavity.

[0046] Furthermore, the concentration of potassium hydroxide is preferably 0.5~2 M, for example, including but not limited to any point value or any range of two points from 0.5 M, 0.8 M, 1 M, 1.5 M, 1.8 M and 2 M.

[0047] Furthermore, the concentration of the tetrahydroquinoxaline is preferably 10-20 mM, for example, including but not limited to any point value or any range of two points such as 10 mM, 12 mM, 15 mM, 18 mM and 20 mM.

[0048] Furthermore, the electrolyte for catalytic dehydrogenation of tetrahydroquinoxaline may also contain dioxane, wherein the concentration of dioxane is preferably 8 vol% to 12 vol%, for example, including but not limited to any point value or any two points of 8 vol%, 9 vol%, 10 vol%, 11 vol%, and 12 vol%.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention modifies conventional CoNi / NF catalysts with phosphorus or fluorine to prepare CoNiP / NF and CoNiF / NF catalysts, which are then used as working electrodes to catalyze the hydrogenation of quinoxaline or the dehydrogenation of tetrahydroquinoxaline. This further improves the conversion rate and selectivity of the reaction, suppresses side reactions, exhibits strong electrochemical stability, enhances the long-term service performance as an electrode, and demonstrates good process compatibility and scalability. It has significant engineering practical value for promoting the industrialization of hydrogen energy storage and transportation technology. Attached Figure Description

[0050] Figure 1 The figures show the GC curves for the hydrogenation of quinoxaline catalyzed by the CoNi / NF catalyst. In the figures, a represents the GC detection results for the first catalytic hydrogenation reaction of quinoxaline catalyzed by the CoNi / NF catalyst; b represents the GC detection results for the second catalytic hydrogenation reaction of quinoxaline catalyzed by the CoNi / NF catalyst.

[0051] Figure 2 The images show the SEM results of five catalytic hydrogenation reactions of quinoxaline using the CONi / NF catalyst in the experimental electrolyte (water + 1 M potassium hydroxide + 15 mM quinoxaline). Image a is a low-magnification SEM image with a scale bar of 100 μm; image b is a medium-magnification SEM image with a scale bar of 50 μm; and image c is a high-magnification SEM image with a scale bar of 5 μm.

[0052] Figure 3The figures show the GC curves of the tetrahydroquinoxaline dehydrogenation reaction catalyzed by the CoNi / NF catalyst. In the figures, a represents the GC detection results of the first catalytic reaction of tetrahydroquinoxaline dehydrogenation with the CoNi / NF catalyst at 2 h and 3 h; b represents the GC detection results of the second catalytic reaction of tetrahydroquinoxaline dehydrogenation with the CoNi / NF catalyst at 3 h.

[0053] Figure 4 The images show the SEM and EDS results of five catalytic dehydrogenation reactions of tetrahydroquinoxaline using the CONi / NF catalyst in the experimental electrolyte (water + 1 M potassium hydroxide + 15 mM tetrahydroquinoxaline). Image a is a low-magnification SEM image with a scale bar of 100 μm; image b is a medium-magnification SEM image with a scale bar of 50 μm; image c is a high-magnification SEM image with a scale bar of 5 μm; image d shows the O element distribution; image e shows the Ni element distribution; and image f shows the Co element distribution.

[0054] Figure 5 LSV curves for the hydrogenation of quinoxaline catalyzed by CoNiP / NF-1 catalyst.

[0055] Figure 6 LSV curves of the hydrogenation reaction of quinoxaline catalyzed by CoNiP / NF-2 catalyst.

[0056] Figure 7 LSV curves for the hydrogenation of quinoxaline catalyzed by CoNiP / NF-3 catalyst.

[0057] Figure 8 GC curves of the hydrogenation reaction of quinoxaline catalyzed by CoNiP / NF-1 catalyst.

[0058] Figure 9 GC curves of the hydrogenation reaction of quinoxaline catalyzed by CoNiP / NF-2 catalyst.

[0059] Figure 10 GC curves of the hydrogenation reaction of quinoxaline catalyzed by CoNiP / NF-3 catalyst.

[0060] Figure 11 The LSV curves for the dehydrogenation of tetrahydroquinoxaline catalyzed by the CoNiP / NF-1 catalyst are shown.

[0061] Figure 12 The LSV curves for the dehydrogenation reaction of tetrahydroquinoxaline catalyzed by CoNiP / NF-2 catalyst are shown.

[0062] Figure 13 The LSV curves are for the dehydrogenation reaction of tetrahydroquinoxaline catalyzed by CoNiP / NF-3 catalyst. a represents the first LSV test with or without tetrahydroquinoxaline; b represents the third LSV test with tetrahydroquinoxaline.

[0063] Figure 14 GC curves for the dehydrogenation of tetrahydroquinoxaline catalyzed by CoNiP / NF-1 catalyst.

[0064] Figure 15 GC curves for the dehydrogenation reaction of tetrahydroquinoxaline catalyzed by CoNiP / NF-2 catalyst.

[0065] Figure 16 GC curves for the dehydrogenation reaction of tetrahydroquinoxaline catalyzed by CoNiP / NF-3 catalyst.

[0066] Figure 17 The LSV curves of the CoNiF / NF-1 catalyst in the catalytic hydrogenation of quinoxaline are shown.

[0067] Figure 18 LSV curves for the hydrogenation of quinoxaline catalyzed by CoNiF / NF-2, CoNiF / NF-3 and CoNiF / NF-4 catalysts.

[0068] Figure 19 LSV curves for the hydrogenation of quinoxaline catalyzed by CoNiF / NF-3 and CoNiF / NF-5 catalysts.

[0069] Figure 20 GC analysis results for the hydrogenation reaction of quinoxaline catalyzed by CoNiF / NF-1 catalyst.

[0070] Figure 21 GC analysis results for the hydrogenation reaction of quinoxaline catalyzed by CoNiF / NF-3 catalyst.

[0071] Figure 22 GC analysis results for the hydrogenation reaction of quinoxaline catalyzed by CoNiF / NF-5 catalyst.

[0072] Figure 23 Linear sweep voltammetry (LSV) curves for the dehydrogenation of tetrahydroquinoxaline catalyzed by CoNiF / NF-1 catalyst are shown. In the figure, a represents the result of one LSV test with and without tetrahydroquinoxaline; b represents the result of four LSV tests with tetrahydroquinoxaline.

[0073] Figure 24 Linear sweep voltammetry curves for the dehydrogenation reaction of tetrahydroquinoxaline catalyzed by CoNiF / NF-5 catalyst.

[0074] Figure 25 GC analysis results for the dehydrogenation reaction of tetrahydroquinoxaline catalyzed by CoNiF / NF-1 catalyst.

[0075] Figure 26 GC analysis results for the dehydrogenation reaction of tetrahydroquinoxaline catalyzed by CoNiF / NF-5 catalyst.

[0076] Figure 27 Results on the conversion and selectivity of the hydrogenation reaction of quinoxaline catalyzed by CoNiF / NF-5 catalyst.

[0077] Figure 28 The conversion and selectivity results for the dehydrogenation of tetrahydroquinoxaline catalyzed by the CoNiF / NF-5 catalyst are presented. Detailed Implementation

[0078] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Unless otherwise specified, other materials and reagents used in the embodiments are commercially available.

[0079] Example 1 1. Preparation of CoNi / NF supported catalysts As shown in Table 1, the electrolyte was prepared. 190 g of choline chloride and 200 mL of propylene glycol were weighed, with a molar ratio of choline chloride to propylene glycol of 1:2. The mixture was stirred at 45 °C until completely dissolved and a deep eutectic solvent (labeled "blank DES") was formed. Then, cobalt chloride hexahydrate (final concentration 0.2 M), nickel chloride hexahydrate (final concentration 0.2 M), and citric acid (final concentration 0.7 M) were added sequentially to the deep eutectic solvent. The mixture was magnetically stirred at 500 r / min at 45 °C overnight (12 h) until all components were dissolved, yielding the electrolyte for preparing the CoNi / NF catalyst (i.e., the electrolyte used for in-situ electrodeposition).

[0080] Table 1. Composition of the electrolyte used to prepare the CoNi / NF catalyst Cut the nickel foam (NF) to the required size (1×1cm). 2 NF was ultrasonically soaked in 1 mol / L HCl solution for 5 min to etch and remove the oxide layer and passivation film on the NF surface. Then, it was ultrasonically cleaned three times alternately with deionized water and anhydrous ethanol until the pH value was neutral, with each cleaning lasting 5 min to remove surface oil and organic impurities. Finally, it was thoroughly dried in a vacuum or forced-air drying oven at 60℃ to obtain clean, surface-activated pretreated NF.

[0081] In-situ electrodeposition was performed using chronoamperometry, with pretreated NF as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode. The electrolyte was the same electrolyte used to prepare the CoNi / NF catalyst. Electrodeposition was carried out at a constant potential of -1.2 V vs. SCE for 2 h using a Metrohm Autolab PGSTAT302N electrochemical workstation, maintained at a constant temperature of 40 °C, and magnetically stirred (500 r / min) to obtain the CoNi / NF catalyst. After the reaction, the catalyst was rinsed with ultrapure water and dried at 60 °C for later use.

[0082] 2. Effect of CoNi / NF catalyst on the hydrogenation of quinoxaline The composition and relevant parameters of the electrochemical system for the hydrogenation of quinoxaline catalyzed by CoNi / NF catalyst are shown in Table 2. An H-type electrolyzer was used, with the anion exchange membrane placed between the flanges of the two halves of the H-type electrolyzer. Rubber sealing gaskets were placed on both sides of the membrane, and the flange bolts were tightened to seal it, thus dividing the electrolyzer into a cathode chamber and an anode chamber. The working electrode and reference electrode were placed in the cathode chamber, and the counter electrode was placed in the anode chamber. The CoNi / NF catalyst was then placed in the (-) (quinoxaline / tetrahydroquinoxaline) |water + 1 M potassium hydroxide + 15 mM quinoxaline||water + 1 M potassium hydroxide|Pt(OH) - Chronoamperometry was performed in the / O2)(+) system. A Metrohm Autolab PGSTAT302N electrochemical workstation was used, with the potential set to -0.3 V (vs. RHE), and the temperature maintained at 40℃. Magnetic stirring (500 r / min) was employed to catalyze the hydrogenation reaction of quinoxaline. The electrolytes before and after the hydrogenation reaction were collected, and the effectiveness of the hydrogenation reaction was verified by gas chromatography (GC). An Agilent Technologies 7890B GC System was used for GC detection. The column oven temperature was 130℃, the inlet temperature was 200℃, and the temperature was maintained at 130℃ for 5 min after injection, then increased to 210℃ at a rate of 15℃ / min and held for 10 min to obtain the gas chromatogram.

[0083] Table 2. Composition and related parameters of the electrochemical system for the hydrogenation of quinoxaline catalyzed by CoNi / NF catalyst. like Figure 1 a and Figure 1 Figure b shows the GC detection results of the hydrogenation reaction of quinoxaline catalyzed by the CoNi / NF catalyst. After 3 h of the first hydrogenation reaction, the conversion rate reached 99.77% and the selectivity was 83.86%. After 3 h of the second hydrogenation reaction, the conversion rate remained at 99.38%, and the selectivity increased to 86.6%, indicating that the CoNi / NF catalyst has excellent and stable catalytic efficiency and product directing ability.

[0084] like Figure 2 a to Figure 2 As shown in Figure c, after five cycles (3 h each) of catalytic hydrogenation of quinoxaline, the CoNi / NF catalyst was dried and found to have powdery detachment from its surface. Scanning electron microscopy (SEM) revealed significant detachment of the CoNi / NF catalyst from the NF substrate surface, leaving only a few nanocrystal pillars. This indicates that the loss of catalytic activity of the CoNi / NF catalyst is due to the detachment of the catalyst itself, leaving only the NF substrate to function, thus lacking catalytic hydrogenation activity.

[0085] 3. Effect of CoNi / NF catalyst on the dehydrogenation reaction of tetrahydroquinoxaline The composition and relevant parameters of the electrochemical system for the dehydrogenation reaction of tetrahydroquinoxaline catalyzed by CoNi / NF catalyst are shown in Table 3. An H-type electrolyzer was used, with the anion exchange membrane placed between the flanges of the two halves of the H-type electrolyzer. Rubber sealing gaskets were placed on both sides of the membrane, and the flange bolts were tightened to seal it, thus dividing the electrolyzer into a cathode chamber and an anode chamber. The working electrode and reference electrode were placed in the cathode chamber, and the counter electrode was placed in the anode chamber. Chronoamperometry was performed on the CoNi / NF catalyst in the system of (-) (quinoxaline / tetrahydroquinoxaline) |water + 1 M potassium hydroxide + 15 mM tetrahydroquinoxaline||water + 1 M potassium hydroxide| Pt(H2O / H2)(+). A Metrohm Autolab PGSTAT302N electrochemical workstation was used, with the potential set to 1.5 V (vs. RHE), the temperature maintained at 40℃, and magnetic stirring (500 r / min) to catalyze the dehydrogenation reaction of tetrahydroquinoxaline. Collect the electrolyte before and after the tetrahydroquinoxaline dehydrogenation reaction, and verify the effect of the tetrahydroquinoxaline dehydrogenation reaction by gas chromatography (GC). The GC detection method is the same as step 2 of this embodiment.

[0086] Table 3. Composition and related parameters of the electrochemical system for the dehydrogenation reaction of tetrahydroquinoxaline catalyzed by CoNi / NF catalyst. like Figure 3 a and Figure 3 Figure b shows the GC detection results of the tetrahydroquinoxaline dehydrogenation reaction catalyzed by the CoNi / NF catalyst. First catalytic tetrahydroquinoxaline dehydrogenation reaction: After 2 h, the reaction completion rate was 81.57%, and the selectivity was 58.8%. After 3 h, the reaction completion rate was 94.65%, and the selectivity was 66.2%. Second catalytic tetrahydroquinoxaline dehydrogenation reaction: After 3 h, the reaction completion rate was 96.53%, and the selectivity was 68.45%. No other significant impurity peaks were found in the GC analysis results, proving that tetrahydroquinoxaline was almost completely converted to quinoxaline.

[0087] like Figure 4 a to Figure 4 As shown in f, after five cycles (3 h each) of the catalytic dehydrogenation reaction of tetrahydroquinoxaline, the CoNi / NF catalyst was dried and its surface remained black with no powdery shedding. SEM analysis showed that CoNi / NF catalyst was still attached to the NF substrate surface, but its nanosheet morphology was significantly corroded. EDS spectroscopy showed that the surface of the CoNi / NF catalyst at this time contained only a large amount of Ni element, while Co element was very scarce. This indicates that the catalytic dehydrogenation activity of the CoNi / NF catalyst at this time is essentially due to Ni element as the active site, while Co element has been detached and dissolved during the several tetrahydroquinoxaline dehydrogenation reactions.

[0088] Example 2 1. Preparation of CoNiP / NF catalyst Phosphated CoNi / NF catalysts (CoNiP / NF) were prepared by controlling the amount of sodium hypophosphite used. The effect of the degree of phosphating on the catalyst performance was investigated. Three types of CoNiP / NF were prepared and tested.

[0089] (1) Preparation of CoNiP / NF-1 catalyst The CoNi / NF catalyst prepared in Example 1 (1 cm) 2 The catalyst was placed in a ceramic boat along with 800 mg of sodium hypophosphite (NaH2PO2) and heated to 300 °C at a heating rate of 5 °C / min under an argon (Ar) atmosphere. The temperature was maintained at this temperature for 3 h and then allowed to cool naturally to obtain the CoNiP / NF-1 catalyst.

[0090] (2) Preparation of CoNiP / NF-2 catalyst Electrochemical activation of CoNiP / NF-1 catalyst: The CoNiP / NF-1 catalyst was treated using cyclic voltammetry, with a counter electrode of 1 × 1 cm⁻¹. 2 A platinum sheet was used, with CoNiP / NF-1 as the working electrode. The electrolyte was water + 1 M potassium hydroxide (35 mL). An H-type electrolytic cell was used. The test potential range was set from the open circuit potential to -0.45 V (vs. RHE). The scan rate was 100 mV / s, and a total of 50 cyclic scans were performed to obtain the electrochemically activated CoNiP / NF catalyst (CoNiP / NF-2 catalyst).

[0091] (3) Preparation of CoNiP / NF-3 catalyst The mass of sodium hypophosphite (NaH2PO2) was adjusted to 400 mg, and the other preparation methods were the same as those for preparing CoNiP / NF-1, thus obtaining the CoNiP / NF-3 catalyst precursor. The CoNiP / NF-3 catalyst precursor was then electrochemically activated according to the method for preparing the CoNiP / NF-2 catalyst to obtain the electrochemically activated CoNiP / NF catalyst (CoNiP / NF-3 catalyst).

[0092] 2. Hydrogenation catalytic effect of CoNiP / NF catalyst The CoNi / NF catalyst was replaced with CoNiP / NF-1, CoNiP / NF-2, and CoNiP / NF-3 catalysts, respectively. Other methods were the same as in Example 1. The quinoxaline hydrogenation reaction was catalyzed and detected by GC. In addition, the test potential range was adjusted to an open circuit potential of -0.42 V (vs. RHE) and the scan rate was 5 mV / s for linear sweep voltammetry (LSV) detection.

[0093] (1) LSV detection results ①CoNiP / NF-1: such as Figure 5 As shown, the hydrogen evolution reaction activity of the CoNiP / NF-1 catalyst was not significantly inhibited after the introduction of phosphorus, indicating that the phosphating process did not weaken its basic electrocatalytic performance. Furthermore, the introduction of quinoxaline into the electrochemical system significantly enhanced the current density, confirming that the CoNiP / NF catalyst maintained good catalytic activity for the hydrogenation of quinoxaline after phosphating.

[0094] ②CoNiP / NF-2: such as Figure 6 As shown, the hydrogen evolution reaction (HER) activity of the CoNiP / NF-2 catalyst remained essentially unchanged after the introduction of phosphorus and electrochemical activation. Furthermore, the introduction of quinoxaline into the electrochemical system significantly increased the current density. The electrochemical activation process effectively exposed more Ni / Co active sites, thereby greatly enhancing the catalyst's adsorption capacity for quinoxaline molecules and accelerating the interfacial kinetics of the quinoxaline hydrogenation reaction.

[0095] ③CoNiP / NF-3 catalyst: such as Figure 7 As shown, even after reducing the amount of sodium hypophosphite, the CoNiP / NF-3 catalyst still maintained high hydrogen evolution reaction (HER) activity, indicating that moderate phosphating did not significantly inhibit its intrinsic electrocatalytic performance. Furthermore, the introduction of quinoxaline into the electrochemical system resulted in a significant increase in current density, suggesting that reducing the degree of phosphating further enhanced the activity of the CoNiP / NF-3 catalyst in catalyzing the hydrogenation of quinoxaline.

[0096] (2) GC detection results ①CoNiP / NF-1 catalyst: such as Figure 8 As shown, after 3 hours of reaction, the conversion rate reached 92.23% and the selectivity was 63.71%. The electrolyte was not completely clear after the reaction, but was slightly turbid.

[0097] ②CoNiP / NF-2 catalyst: such as Figure 9 As shown, after 3 hours of reaction, the conversion rate reached 91.02%, the selectivity was 56.74%, the electrolyte became slightly turbid, and there was a white oily substance on the surface.

[0098] ③CoNiP / NF-3 catalyst: such as Figure 10 As shown, after 3 hours of reaction, the conversion rate reached 84.77% and the selectivity was 67.99%.

[0099] The results demonstrate that the catalyst prepared by moderate phosphating combined with electrochemical activation has good hydrogenation catalytic performance and can achieve efficient hydrogenation conversion of the substrate. Compared with the CoNi / NF catalyst, the activity of CoNiP / NF in catalyzing the hydrogenation reaction of quinoxaline is slightly reduced, but it can still meet the operating conditions required for catalyzing the hydrogenation reaction of quinoxaline.

[0100] 3. Dehydrogenation catalytic effect of CoNiP / NF catalyst The CoNi / NF catalyst was replaced with CoNiP / NF-1, CoNiP / NF-2, and CoNiP / NF-3 catalysts, respectively, and the other methods were the same as in Example 1. The tetrahydroquinoxaline dehydrogenation reaction was catalyzed and detected by GC. In addition, the test potential range was adjusted to an open circuit potential of 1.55 V (vs. RHE) and the scan rate was 5 mV / s for linear sweep voltammetry (LSV) detection.

[0101] (1) LSV detection results ①CoNiP / NF-1 catalyst: such as Figure 11 As shown, the introduction of phosphorus weakens the oxygen evolution side reaction activity of the CoNiP / NF-1 catalyst, effectively reducing the interference of competing reactions. The introduction of tetrahydroquinoxaline into the electrochemical system significantly increases the current density, verifying the high catalytic efficiency of the CoNiP / NF-1 catalyst in the dehydrogenation reaction of tetrahydroquinoxaline.

[0102] ②CoNiP / NF-2 catalyst: such as Figure 12 As shown, after introducing phosphorus and undergoing electrochemical activation, the CoNiP / NF-2 catalyst still maintains excellent catalytic activity for the dehydrogenation of tetrahydroquinoxaline, and exhibits a slower current decay in the constant potential test, indicating that its structural stability and anti-poisoning ability have been significantly improved.

[0103] ③CoNiP / NF-3 catalyst: such as Figure 13 a and Figure 13 As shown in b, even after reducing the amount of sodium hypophosphite, the CoNiP / NF-3 catalyst still exhibits high initial catalytic activity in the dehydrogenation of tetrahydroquinoxaline, with a dehydrogenation current density reaching 118 mA cm⁻¹. -2 However, in three consecutive linear sweep voltammetry (LSV) tests, the catalytic current of the electrode showed a significant decrease, indicating that its resistance to poisoning and cycling stability still need further improvement. This result suggests that lower phosphorus content is not always more beneficial; while moderate phosphating can balance activity and stability, insufficient phosphating still fails to effectively inhibit the deterioration and deactivation of active sites on the electrode surface during the reaction process.

[0104] (2) GC detection results ①CoNiP / NF-1 catalyst: such as Figure 14 As shown, after 3 hours of reaction, the conversion rate was 87.94% and the selectivity was 45.96%. No other significant impurity peaks were found in the GC detection results, proving that tetrahydroquinoxaline was almost completely converted to quinoxaline, but the selectivity was not high.

[0105] ②CoNiP / NF-2 catalyst: such as Figure 15 As shown, after 3 hours of reaction, the conversion rate was 99.65% and the selectivity was 95.56%. No other significant impurity peaks were found in the GC detection results, proving that tetrahydroquinoxaline was almost completely converted to quinoxaline.

[0106] ③CoNiP / NF-3 catalyst: such as Figure 16 As shown, after 3 hours of reaction, the conversion rate was 67.81% and the selectivity was 47.65%.

[0107] The results demonstrate that the undoped CoNi / NF catalyst exhibits a dehydrogenation conversion rate of 96.53% and a target product selectivity of 68.45%. After phosphorus doping modification, the CoNiP / NF-2 catalyst achieves a dehydrogenation conversion rate of 99.65% and a target product selectivity of 95.56%. Moderate phosphating combined with electrochemical activation significantly enhances catalyst performance, effectively increasing the substrate dehydrogenation conversion and significantly suppressing side reactions, thereby greatly improving the directional catalytic performance of the dehydrogenation reaction.

[0108] Regarding phosphorus modification, the CoNiP / NF-1 catalyst prepared by thermal phosphating maintained good initial catalytic activity in both hydrogenation and dehydrogenation, indicating that phosphating treatment did not significantly weaken its basic electrocatalytic performance and could enhance the structural stability of the material to some extent. However, the reaction results showed that CoNiP / NF-1 still exhibited electrolyte turbidity and low selectivity during the hydrogenation of quinoxaline, indicating that although phosphorus modification helps to construct a stable active phase, it is still insufficient in inhibiting the formation of byproducts and interface degradation.

[0109] The CoNiP / NF-2 electrode obtained by further electrochemical activation based on thermal phosphating exhibited superior stability in hydrogenation and dehydrogenation. Specifically, the current decay was slower in the dehydrogenation reaction, and the dehydrogenation conversion and selectivity of tetrahydroquinoxaline reached 99.65% and 95.56%, respectively. This indicates that electrochemical activation helps expose more effective Ni / Co active sites and improves the interfacial state of the catalyst layer surface, thereby enhancing the electrode's resistance to degradation. These results demonstrate that the thermal phosphating + electrochemical activation method has a positive effect on improving electrode stability and inhibiting degradation.

[0110] The above experimental results evaluated the performance of different CoNiP / NF-based catalysts for the electrochemical hydrogenation and electrochemical dehydrogenation of quinoxaline. This invention utilizes moderate phosphating combined with electrochemical activation to significantly improve catalyst performance. When applied to the hydrogenation and dehydrogenation reactions of nitrogen heterocyclic compounds, it significantly improves reaction conversion and target product selectivity, with the most significant improvement in dehydrogenation performance. This indicates that this invention can fulfill the dual-function catalysis requirement for the directed hydrogenation and dehydrogenation of nitrogen heterocyclic compounds, and is suitable for hydrogenation and dehydrogenation catalytic reaction scenarios.

[0111] Example 3 1. Preparation of CoNiF / NF catalyst By incorporating fluorine (F) into CoNi / NF catalysts, CoNiF / NF catalysts were prepared, and the effect of the degree of fluorination on catalyst performance was investigated. Five CoNiF / NF catalysts were prepared and tested.

[0112] (1) Preparation of CoNiF / NF-1 catalyst 0.1 M ammonium fluoride was added to the electrolyte in Table 1 of Example 1, and the rest of the preparation method of CoNi / NF catalyst was the same as in Example 1 to obtain CoNiF / NF-1 catalyst.

[0113] (2) Preparation of CoNiF / NF-2 catalyst The amount of ammonium fluoride in the electrolyte of the CoNiF / NF-1 catalyst was adjusted to 0.05 M, and the other preparation methods were the same as those for the CoNiF / NF-1 catalyst, thus obtaining the CoNiF / NF-2 catalyst.

[0114] (3) Preparation of CoNiF / NF-3 catalyst The electrodeposition voltage was adjusted to -1.25 V vs. SCE, and the other preparation methods were the same as those used to prepare the CoNiF / NF-2 catalyst, thus obtaining the CoNiF / NF-3 catalyst.

[0115] (4) Preparation of CoNiF / NF-4 supported catalyst The electrodeposition voltage was adjusted to -1.3 V vs. SCE, and the other preparation methods were the same as those used to prepare the CoNiF / NF-2 catalyst, thus obtaining the CoNiF / NF-4 catalyst.

[0116] (5) Preparation of CoNiF / NF-5 supported catalyst The electrodeposition time was adjusted to 1 h, and the other preparation methods were the same as those used to prepare the CoNiF / NF-3 catalyst, thus obtaining the CoNiF / NF-5 catalyst.

[0117] 2. Effect of CoNiF / NF catalyst on the hydrogenation reaction of quinoxaline (1) The CoNi / NF catalyst was replaced with CoNiF / NF-1, CoNiF / NF-2, CoNiF / NF-3, CoNiF / NF-4, and CoNiF / NF-5 catalysts, respectively. The composition and related parameters of other electrochemical systems were the same as in Example 1. The quinoxaline hydrogenation reaction was catalyzed. In addition, the test potential range was adjusted to the open circuit potential of -0.42 V (vs. RHE) and the scan rate was 5 mV / s for linear sweep voltammetry (LSV) test.

[0118] Doping Co-Ni alloy lattices with fluorine can modulate the electronegativity of the catalyst, thereby weakening its adsorption capacity for quinoxaline molecules. This characteristic is specifically manifested in linear sweep voltammetry (LSV) testing as follows: Figure 17 In the control group electrolyte, the hydrogen evolution reaction current did not show a significant decrease; however, when 15 mM quinoxaline was introduced into the electrolyte, the current density of the catalytic system showed a slight decrease, which is consistent with the regulatory effect of fluorine modification on the adsorption of reactants.

[0119] like Figure 18 As shown, the three catalysts CoNiF / NF-2, CoNiF / NF-3, and CoNiF / NF-4 exhibited higher catalytic hydrogenation activity. Among them, CoNiF / NF-3 had a larger net reaction current and was superior among the three CoNiF / NF catalysts with different electrodeposition voltages.

[0120] like Figure 19 As shown, to address the issue that the CoNiF / NF catalyst exhibits significant hydrogen evolution reaction activity under high overpotential conditions, and that the vigorous bubble evolution process may cause mechanical damage to the catalyst structure, this invention prepares a CoNiF / NF-5 catalyst by controlling the electrodeposition time. Linear sweep voltammetry results show that, compared to the CoNiF / NF-3 catalyst obtained by electrodeposition for 2 h, the CoNiF / NF-5 catalyst exhibits a lower hydrogen evolution reaction current density, which helps to mitigate the damage to the catalyst structure caused by hydrogen evolution side reactions, thereby improving the structural stability of the electrode during electrochemical hydrogenation.

[0121] (2) Replace the CoNi / NF catalyst with CoNiF / NF-1, CoNiF / NF-3 and CoNiF / NF-5 catalysts respectively, and follow the same procedure as in Example 1 to catalyze the hydrogenation reaction of quinoxaline and perform GC detection.

[0122] CoNiF / NF-1 catalyst: such as Figure 20 As shown, after 3 hours of reaction, the conversion rate reached 95.83% and the selectivity was 100%.

[0123] CoNiF / NF-3 catalyst: such as Figure 21 As shown, after 3 hours of reaction, the conversion rate reached 96.61%, and the reaction selectivity was 100%. The electrolyte was clear, with no white substances appearing, and no dihydroquinoxaline was detected in the GC analysis results, demonstrating excellent reaction selectivity.

[0124] CoNiF / NF-5 catalyst: such as Figure 22 As shown, after 3 hours of reaction, the conversion rate reached 96.16%, and the reaction selectivity was 100%. Simultaneously, the electrolyte was clear, with no white substances appearing, and GC analysis revealed no dihydroquinoxaline, demonstrating excellent reaction selectivity. Furthermore, no significant catalyst detachment occurred after multiple hydrogen additions.

[0125] The results demonstrate that, compared to the undoped CoNi / NF electrode, the CoNiF / NF-5 catalyst of this invention still maintains a high conversion level of over 96%; fluorine modification significantly optimizes the selectivity of the catalyst's active sites, increasing the selectivity of the target product to 100%, and completely suppressing side reactions and excessive hydrogenation behavior.

[0126] 3. The effect of CoNiF / NF catalyst on the dehydrogenation of tetrahydroquinoxaline (1) The CoNi / NF catalyst was replaced with CoNiF / NF-1 and CoNiF / NF-5 catalysts respectively. The composition and related parameters of other electrochemical systems were the same as in Example 1. The tetrahydroquinoxaline dehydrogenation reaction was catalyzed. The test potential range was set from the open circuit potential to 1.55 V (vs. RHE), the scan rate was 5 mV / s, and linear sweep voltammetry (LSV) was performed.

[0127] like Figure 23 a and Figure 23As shown in b, the fluorinated CoNiF / NF-1 catalyst exhibits significantly enhanced catalytic performance in the dehydrogenation of tetrahydroquinoxaline. The introduction of tetrahydroquinoxaline into the reaction system significantly increased the current density, confirming the high catalytic activity of CoNiF / NF-1 for the dehydrogenation of tetrahydroquinoxaline. Furthermore, fluorine induces a redistribution of the electronic structure on the surface of the CoNiF / NF-1 catalyst, enhancing electronegativity and optimizing the adsorption behavior of nitrogen-containing heterocyclic substrates, effectively mitigating the excessive adsorption and accumulation of reaction intermediates at the active sites. Therefore, in four LSV tests, the CoNiF / NF-1 catalyst exhibited a low current density decay rate and excellent cycling stability, demonstrating good resistance to poisoning and deactivation.

[0128] like Figure 24 As shown, the CoNiF / NF-5 catalyst also exhibits excellent catalytic performance in the electrochemical dehydrogenation reaction of tetrahydroquinoxaline. At an applied potential of 1.55 V (vs. RHE), the oxygen evolution competing reaction current density of this electrode is only 16 mA·cm⁻¹. -2 The current density of the tetrahydroquinoxaline dehydrogenation reaction is as high as 87 mA·cm. -2 The dehydrogenation current density of the CoNiF / NF-5 catalyst was significantly stronger than that of the oxygen evolution reaction, indicating that it possesses highly efficient selective catalytic activity for the dehydrogenation of tetrahydroquinoxaline. Although the electrodeposition amount of the CoNiF / NF-5 catalyst was reduced compared to the CoNiF / NF-3 catalyst, its dehydrogenation current density did not show a significant decrease and remained at a high level, indicating that moderately reducing the catalyst loading has a limited impact on the dehydrogenation activity. This result further confirms that by controlling the deposition time and optimizing the catalyst structure, the competitive oxygen evolution reaction can be effectively suppressed while maintaining high dehydrogenation activity, which is beneficial to improving the Faraday efficiency of the target reaction.

[0129] (2) The CoNi / NF catalyst was replaced with CoNiF / NF-1 and CoNiF / NF-5 catalysts respectively. Other methods were the same as in Example 1. The tetrahydroquinoxaline dehydrogenation reaction was catalyzed and GC analysis was performed.

[0130] CoNiF / NF-1 catalyst: such as Figure 25 As shown, after 3 hours of reaction, the reaction completion rate was 83.52% and the reaction selectivity was 81.14%.

[0131] CoNiF / NF-5 catalyst: such as Figure 26 As shown, after 3 hours of reaction, the reaction completion rate reached 89.93%, and the reaction selectivity was 100%.

[0132] The results showed that the unmodified CoNi / NF catalyst had high intrinsic dehydrogenation activity and sufficient substrate conversion, but due to the excessive number of highly active sites on the surface, it was prone to side reactions such as substrate ring opening and deep cracking, resulting in a target product selectivity of only 68.45%. After fluorine modification, the surface active sites of the CoNiF / NF-5 catalyst were precisely regulated, and while maintaining a high dehydrogenation conversion rate of 89.93%, the side reaction pathways were completely eliminated, and the target product selectivity was increased to 100%, achieving highly selective directional catalysis of the dehydrogenation reaction.

[0133] Fluorine doping can reduce the excessive adsorption of quinoxaline and its intermediates by the catalyst by modulating the electronegativity and surface adsorption behavior of CoNi alloys, thereby reducing the risk of active site poisoning and inhibiting structural degradation caused by intermediate accumulation.

[0134] Different fluorine concentrations, deposition potentials, and deposition times significantly affect electrode stability. Among them, the CoNiF / NF-3 catalyst exhibited a larger net reaction current in the hydrogenation reaction of quinoxaline, with a conversion rate of 96.61% and a selectivity of 100%. Moreover, the electrolyte remained clear, and no white byproducts appeared, indicating that appropriate fluorine doping can effectively suppress side reactions and intermediate accumulation, thereby mitigating the interfacial degradation caused by byproduct formation.

[0135] To address the potential mechanical damage to the catalyst caused by severe gas evolution during the cathode hydrogen evolution reaction (HER) at high overpotentials, a CoNiF / NF-5 catalyst was prepared as an electrode by shortening the deposition time. Results showed that this electrode maintained high hydrogenation and dehydrogenation activity while significantly reducing the HER current, helping to mitigate the impact and stripping risk of gas evolution on the catalyst layer. No significant catalyst stripping occurred after multiple hydrogenation cycles, and the competing current for the anolyte hydrogen evolution reaction (OER) during dehydrogenation was much lower than the target dehydrogenation current, indicating that the fluorine doping + deposition time method can simultaneously suppress gas-induced mechanical degradation and the Faradaic efficiency loss caused by competing side reactions.

[0136] This invention utilizes the strong electronegativity of fluorine to regulate surface electron distribution, effectively mitigating excessive adsorption of organic species. Using a CoNiF / NF-3 catalyst as an electrode, a 96.61% conversion and 100% selectivity were achieved in the quinoxaline hydrogenation reaction after 3 hours. To further enhance the electrode's structural stability, a CoNiF / NF-5 electrode was prepared by optimizing the electrodeposition time (from 2 hours to 1 hour). While maintaining high hydrogenation activity (96.16% conversion and 100% selectivity) and high dehydrogenation activity (89.93% conversion and 100% selectivity), this electrode significantly suppressed the mechanical damage to the catalyst structure caused by side reactions, exhibiting superior corrosion resistance and long-term operational potential.

[0137] Example 4 1. Using an H-type electrolytic cell, place the anion exchange membrane between the flanges of the two halves of the H-type electrolytic cell. Place rubber sealing gaskets on both sides of the membrane, tighten the flange bolts to seal, thus dividing the electrolytic cell into a cathode chamber and an anode chamber. The working electrode and reference electrode are placed in the cathode chamber, and the counter electrode is placed in the anode chamber. CoNiF / NF-5 is placed in (-) (quinoxaline / tetrahydroquinoxaline)|1 M potassium hydroxide + 10 vol% dioxane + 15 mM quinoxaline||water + 1 M potassium hydroxide| Pt(OH) - Chronoamperometry was performed in the / O2)(+) system using a Metrohm Autolab PGSTAT302N electrochemical workstation. The potential was set to -0.25 V (vs. RHE), the temperature was maintained at 40℃, and magnetic stirring (500 r / min) was used to catalyze the hydrogenation reaction of quinoxaline. The composition and relevant parameters of the long-cycle electrochemical system for the hydrogenation reaction of quinoxaline catalyzed by CoNiF / NF-5 catalyst are shown in Table 4.

[0138] Table 4. Composition and related parameters of the long-cycle electrochemical system for the hydrogenation of quinoxaline catalyzed by CoNiF / NF-5 catalyst. like Figure 27 As shown, 14 repeated experiments of quinoxaline hydrogenation reaction were carried out using CoNiF / NF-5 catalyst as working electrode, each lasting 50 h. GC detection showed that the conversion rate was stable at 78.5%~97.6% (reaching a maximum of 97.63% in the 6th experiment), and the selectivity remained at 100% in all experiments, proving that the catalyst has excellent selectivity and long-term stability in the optimized system.

[0139] 2. An H-type electrolytic cell was used. The anion exchange membrane was placed between the flanges of the two halves of the H-type electrolytic cell, and rubber sealing gaskets were placed on both sides of the membrane. The flange bolts were tightened to seal the membrane, thus dividing the electrolytic cell into a cathode chamber and an anode chamber. The working electrode and reference electrode were placed in the cathode chamber, and the counter electrode was placed in the anode chamber. The chronoamperometry of CoNiF / NF-5 in the (-) (quinoxaline / tetrahydroquinoxaline) |1M potassium hydroxide + 10 vol% dioxane + 15 mM tetrahydroquinoxaline||water + 1 M potassium hydroxide| Pt(H2O / H2)(+) system was measured using a Metrohm Autolab PGSTAT302N electrochemical workstation. The potential was set to 1.45 V (vs. RHE), the temperature was kept constant at 40℃, and magnetic stirring (500 r / min) was used to catalyze the dehydrogenation reaction of tetrahydroquinoxaline. The composition and relevant parameters of the electrochemical system for the dehydrogenation reaction of tetrahydroquinoxaline catalyzed by CoNiF / NF-5 catalyst are shown in Table 5.

[0140] Table 5. Composition and relevant parameters of the electrochemical system for the dehydrogenation reaction of tetrahydroquinoxaline catalyzed by CoNiF / NF-5 catalyst. like Figure 28 As shown, in four 50-h dehydrogenation cycle experiments using CoNiF / NF-5 catalyst as the working electrode, GC detection results showed that the conversion rate remained stable above 52.17% and the selectivity remained above 64.6% (100% in the first and third cycles). The high conversion rate and selectivity indicate that the CoNiF / NF-5 electrode has good electrochemical stability under long-cycle dehydrogenation conditions.

[0141] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a non-metallic modified nickel-cobalt catalyst, characterized in that, The CoNi / NF catalyst is modified with a nonmetal, including phosphorus or fluorine. In-situ electrodeposition was performed using nickel foam as a substrate. The electrolyte used for in-situ electrodeposition contained cobalt ions and nickel ions to obtain a CoNi / NF catalyst. When the non-metal is phosphorus, the CoNi / NF catalyst is mixed with a phosphorus source and heat-treated at 250~350℃ for 2~4 h in an inert gas atmosphere to obtain the CoNiP / NF catalyst. When the non-metal is fluorine, in-situ electrodeposition is performed using nickel foam as a substrate. The electrolyte used for in-situ electrodeposition contains cobalt ions, nickel ions, and fluorine ions to obtain the CoNiF / NF catalyst.

2. The preparation method according to claim 1, characterized in that, The concentration of the cobalt ions is 0.1~0.3 M; And / or, the concentration of the nickel ions is 0.1~0.3 M; And / or, the concentration of the fluoride ions is 0.05~0.1 M.

3. The preparation method according to claim 1, characterized in that, The voltage for the in-situ electrodeposition is -1.1 to -1.3 V vs. SCE; And / or, the in-situ electrodeposition time is 1~3 h.

4. The preparation method according to claim 1, characterized in that, The electrolyte also contains choline chloride and propylene glycol.

5. The preparation method according to claim 1, characterized in that, The phosphorus source includes sodium hypophosphite, and the ratio of the CoNi / NF catalyst to sodium hypophosphite is: CoNi / NF catalyst : sodium hypophosphite = 1 cm⁻¹ 2 : (400~800)mg.

6. The preparation method according to claim 1, characterized in that, The CoNiP / NF catalyst was electrochemically activated using cyclic voltammetry to obtain an electrochemically activated CoNiP / NF catalyst.

7. A non-metallic modified nickel-cobalt catalyst, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the non-metallic modified nickel-cobalt catalyst of claim 7 in the catalytic hydrogenation reaction of quinoxaline or the dehydrogenation reaction of tetrahydroquinoxaline.

9. A method for catalytic hydrogenation of quinoxaline, characterized in that, Using the non-metallic modified cobalt nickel catalyst of claim 7 as the working electrode, platinum as the counter electrode, and mercury / mercury oxide as the reference electrode, electrolysis is performed. The electrolyte for catalyzing the hydrogenation of quinoxaline contains water, potassium hydroxide, and quinoxaline.

10. A method for catalytic dehydrogenation of tetrahydroquinoxaline, characterized in that, Using the non-metallic modified cobalt nickel catalyst of claim 7 as the working electrode, platinum as the counter electrode, and mercury / mercury oxide as the reference electrode, electrolysis is performed. The electrolyte for catalyzing the dehydrogenation of tetrahydroquinoxaline contains water, potassium hydroxide, and tetrahydroquinoxaline.

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