Non-noble metal substrate graphite electrode suitable for organic electrosynthesis and preparation method of non-noble metal substrate graphite electrode

Abstract

The invention relates to the technical field of organic electrosynthesis, in particular to a non-noble metal substrate graphite electrode suitable for organic electrosynthesis and a preparation method of the non-noble metal substrate graphite electrode, and the preparation method comprises the steps of substrate layer pretreatment, runner forming, transition coating deposition, functional coating deposition and post-treatment optimization. Nickel, iron, titanium and alloys thereof are selected as base layer materials, and roughening treatment, a diamond-like carbon transition layer and a boron-doped graphite functional coating are combined, so that the mass transfer efficiency and the interface bonding strength of the electrode are remarkably improved. The runner design is optimized, so that the diffusion coefficient of reactants is increased by 30%-50%, the voltage of an electrolytic bath is smaller than or equal to 3.0 V, the current efficiency is larger than or equal to 95%, the service life of an electrode is larger than or equal to 500 hours, and the cost is only 1%-5% of that of a precious metal electrode. The method is suitable for the zero-polar-distance electrolytic cell, and mass transfer requirements of different systems are met.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical synthesis and material preparation, and more particularly to a non-noble metal-based graphite electrode suitable for organic electrosynthesis and a preparation method thereof. Background Art

[0002] Organic electrosynthesis technology achieves efficient synthesis of compounds through electrolytic reactions and is widely used in the chemical, pharmaceutical, and materials fields. Electrodes, as core components in this process, directly influence reaction efficiency, energy consumption, and product selectivity. Therefore, the development of high-performance, low-cost, and easily prepared electrode materials has become a research hotspot in organic electrosynthesis.

[0003] Publication number CN117616158B discloses a method for manufacturing an electrode and an electrode. This patent provides a method for preparing an electrode by heat treatment and acid etching of a nickel-iron alloy substrate, aiming to improve the oxygen evolution reaction (OER) activity without relying on a catalyst coating. However, this technical solution has the following shortcomings: First, its substrate is a nickel-iron alloy, which is a precious metal or transition metal material with a high cost, making it difficult to meet the demand for low-cost non-precious metal substrates in organic electrosynthesis; second, this method is mainly aimed at optimizing the oxygen evolution reaction, and does not fully consider the complex redox reaction environment in organic electrosynthesis, which may lead to insufficient stability and catalytic performance of the electrode in the organic system; finally, this method has high requirements on the composition and treatment process of the substrate, which may increase the difficulty and cost of preparation.

[0004] Publication number CN104937142B discloses a method for manufacturing an electrode for electrolysis. This patent achieves the preparation of a high-performance electrode by coating a starting material liquid containing an electrocatalytic component and forming an electrode catalyst layer on the surface of a conductive substrate. However, this technical solution also has certain limitations: first, its substrate is mainly precious metals or alloys such as titanium and tantalum, which does not meet the requirements of non-precious metal substrates, limiting its application in low-cost organic electrosynthesis; second, this method relies on the preparation of a catalyst coating, which increases process complexity and production costs; in addition, the electrode design is mainly targeted at traditional electrolysis processes and does not fully consider the requirements for mass transfer efficiency and interface stability in organic electrosynthesis, which may lead to insufficient long-term stability of the electrode in organic solvents. Summary of the Invention

[0005] To overcome the above-mentioned defects, the present invention provides a non-precious metal-based graphite electrode suitable for organic electrosynthesis and a preparation method thereof, which can solve the problems in the prior art such as difficulty in reducing electrode thickness, limited flow channel modification, and insufficient mass transfer efficiency, thereby producing an electrode with high mass transfer efficiency, low energy consumption, long life, and economical cost.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A non-precious metal-based graphite electrode suitable for organic electrosynthesis comprises, from bottom to top, a base layer, a roughened layer, a transition coating, and a functional coating. The base layer is made of a non-precious metal material, and its surface undergoes chemical cleaning and mechanical treatment to form a roughened layer. The transition coating has a diamond-like carbon structure and is located between the roughened layer and the functional coating. The functional coating is composed of boron-doped graphite and is formed by low-pressure chemical vapor deposition or physical vapor deposition.

[0008] The base layer of the electrode needs to withstand the corrosion of the electrolyte and the stress of long-term electrochemical reactions during application. In traditional technology, although the carbon fiber base has a certain conductivity, its thickness is difficult to further reduce, and the flexibility of the flow channel design is limited. The present invention uses nickel, iron, titanium and their alloy plates as the base layer material, and its thickness is controlled within the range of 0.1 to 1.5 mm. At the same time, combined with a specific flow channel design, the application of the electrode in the zero-gap electrolytic cell is more flexible.

[0009] The present invention enhances the adhesion of subsequent coatings by roughening the base layer. Specifically, the base layer is first subjected to a chemical cleaning process to remove the surface oxide layer and oil stains: the plate is immersed in a 5% to 10% hydrochloric acid solution, ultrasonically treated at 60 to 80°C for 10 to 30 minutes, then ultrasonically degreased with ethanol, and rinsed with deionized water until neutral. Then, the cleaned base layer is roughened by sandblasting or electrochemical etching. In the sandblasting process, Al2O3 sand or SiO2 quartz sand with a particle size of 50 to 150μm is used, and the air pressure is controlled at 0.3 to 0.6MPa; in the electrochemical etching process, a 1mol / LH2SO4 solution is used, and the current density is 5 to 10mA / cm 2 After the above treatment, the surface roughness Ra of the substrate layer reaches 1.6 to 6.3 μm, which significantly enhances the adhesion of subsequent coatings.

[0010] The present invention also optimizes the mass transfer performance of the electrode by designing a specific flow channel structure. The flow channel type is selected according to the characteristics of the electrolyte: the straight flow channel is suitable for low viscosity systems, the flow channel width is 2 to 5mm, the depth is 1 to 3mm, and the flow rate is not less than 5mL / s; the serpentine / S-shaped flow channel enhances turbulence through a 60° to 120° bending angle design, and the flow channel spacing is 2 to 8mm, which is suitable for high viscosity electrolytes; the porous array flow channel is formed by stamping a porous structure with a pore size of 0.5 to 2mm and a pore spacing of 2 to 5mm to promote three-dimensional mass transfer. The stamping process parameters are: punch temperature 50 to 80℃, pressure 5 to 20MPa, and holding time 5 to 30 seconds to ensure smooth flow channel edges and dimensional accuracy of ±0.05mm.

[0011] The preparation of the functional coating is one of the core steps of the present invention. The present invention adopts low-pressure chemical vapor deposition (CVD) or physical vapor deposition (PVD) method to form a graphite coating doped with boron on the substrate. In the CVD process, the pretreated substrate is placed in a reaction chamber, and a mixed gas of CH4 and H2 is introduced with a volume ratio of 1:5 to 1:10. When doping with boron, 50 to 200 ppm of trimethylboron (TMB) is introduced. Deposition is carried out at 600 to 900 ° C and 10 to 100 Pa for 1 to 3 hours to form a 3 to 30 μm thick boron-doped carbon / graphite carbon coating. During the deposition process, a 0.5 to 2 μm diamond-like carbon (DLC) transition layer is preferentially generated to improve the interface bonding strength, and the cross-grid test is required to be ≥50 MPa. In the PVD process, sputtering deposition is performed using a graphite target with a purity of ≥99.95% or a B4C target, with an argon pressure of 0.1 to 1 Pa and a power of 100 to 500 W to form a coating with a boron content of 0.5% to 5% at room temperature to 200°C.

[0012] To further optimize electrode performance, the present invention also includes a post-treatment step. The coated electrode is annealed at 300 to 500°C for 1 to 2 hours in a 95% N2 + 5% H2 atmosphere to eliminate internal stress and enhance the degree of graphitization. The Raman spectrum G / D peak intensity ratio is required to be ≥ 2.0. Additionally, a 5% solids PTFE solution can be optionally applied for hydrophobic treatment, achieving a surface contact angle of 90° to 120° and reducing electrolyte retention.

[0013] In the present invention, the thickness of the base layer is 0.1 to 1.5 mm, the surface roughness Ra of the roughened layer is 1.6 to 6.3 μm, the thickness of the transition coating is 0.5 to 2 μm, and the thickness of the functional coating is 3 to 30 μm.

[0014] The present invention also provides a method for preparing the electrode, which comprises the following steps:

[0015] Step 1: Base layer pretreatment

[0016] Nickel, iron, titanium, or their alloys are used as the substrate material, with a thickness ranging from 0.1 to 1.5 mm. The substrate is immersed in a 5% to 10% hydrochloric acid solution and ultrasonically treated at 60 to 80°C for 10 to 30 minutes. It is then ultrasonically degreased with ethanol and rinsed with deionized water until neutral. The cleaned substrate is roughened using sandblasting or electrochemical etching to a surface roughness Ra of 1.6 to 6.3 μm.

[0017] Step 2: Runner molding

[0018] The flow channel type and molding process are selected based on the electrolyte characteristics. Straight-through flow channels are suitable for low-viscosity systems, with a width of 2 to 5 mm and a depth of 1 to 3 mm. Serpentine / S-shaped flow channels enhance turbulence through 60° to 120° bends, with a channel spacing of 2 to 8 mm. Multi-hole array flow channels are stamped to create a porous structure with a pore diameter of 0.5 to 2 mm and a pore spacing of 2 to 5 mm. Stamping process parameters are: punch temperature of 50 to 80°C, pressure of 5 to 20 MPa, and a hold time of 5 to 30 seconds.

[0019] Step 3: Transition coating deposition

[0020] The pretreated substrate layer is placed in a reaction chamber, and a mixed gas of CH4 and H2 (volume ratio 1:5 to 1:10) is introduced. It is deposited at 600 to 900°C and 10 to 100 Pa for 1 to 3 hours to form a diamond-like carbon (DLC) transition layer with a thickness of 0.5 to 2 μm.

[0021] Step 4: Functional coating deposition

[0022] A boron-doped graphite coating is formed on the substrate using low-pressure chemical vapor deposition (CVD) or physical vapor deposition (PVD). During the CVD process, a mixture of CH4 and H2 (volume ratio 1:5 to 1:10) is introduced, along with 50 to 200 ppm of trimethylboron (TMB) for boron doping. Deposition is performed at 600 to 900°C and 10 to 100 Pa for 1 to 3 hours, resulting in a 3 to 30 μm thick boron-doped carbon / graphitic carbon coating. During the PVD process, sputtering is performed using a graphite target (purity ≥ 99.95%) or a B4C target, with an argon pressure of 0.1 to 1 Pa and a power of 100 to 500 W at room temperature to 200°C, to form a coating with a boron content of 0.5 to 5% (atomic fraction).

[0023] Step 5: Post-processing optimization

[0024] The coated electrode is annealed at 300-500°C for 1-2 hours in a 95% N2 + 5% H2 atmosphere to eliminate internal stress and enhance the degree of graphitization (Raman spectrum G / D peak intensity ratio ≥ 2.0). Additionally, a PTFE solution (5% solids content) can be optionally applied for hydrophobic treatment, achieving a surface contact angle of 90° to 120°.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] The electrode prepared by the present invention significantly improves the mass transfer efficiency and interface bonding strength of the electrode by optimizing the base layer material, roughening treatment, flow channel design and coating deposition process. The optimized flow channel structure increases the reactant diffusion coefficient by 30% to 50%, the electrolytic cell voltage is ≤3.0V, which is better than the electrolytic cell voltage of 3.5 to 4.0V of traditional graphite electrodes, and the current efficiency is ≥95%, which is better than the current efficiency of 80% to 85% of traditional electrodes. The interface bonding strength is improved by 2 to 3 times compared with the existing technology, the electrode life is ≥500 hours, which is much longer than the 200 to 300 hours of traditional graphite electrodes, and the cost is only 1% to 5% of that of precious metal electrodes. In addition, the electrode of the present invention is suitable for zero-gap electrolytic cell design, the base layer thickness can be as low as 0.1mm, and the flow channel structure is flexible and adjustable to meet the mass transfer requirements of different reaction systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of the electrode of the present invention.

[0028] Figure 2 It is a top view of the porous array flow channel in the present invention.

[0029] Figure 3 It is a process flow chart of the preparation method of the present invention.

[0030] The reference numerals are as follows:

[0031] 1. Base layer; 2. Roughening layer; 3. Transition coating; 4. Functional coating; 5. Porous array flow channel. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be a central component. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may also be a central component. When a component is considered to be "set on" another component, it may be directly set on the other component or there may also be a central component. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] The present invention provides a non-noble metal-based graphite electrode suitable for organic electrosynthesis, the structure of which is as follows: Figure 1 As shown, it includes a base layer 1, a roughening layer 2, a transition coating 3 and a functional coating 4. The base layer 1 is the basic part of the entire electrode, and its material is selected from nickel, iron, titanium or their alloy plates, and the thickness is controlled in the range of 0.1 to 1.5 mm. The roughening layer 2 is formed on the surface of the base layer 1 by chemical cleaning and mechanical treatment, and its surface roughness Ra reaches 1.6 to 6.3 μm. The transition coating 3 is located between the roughening layer 2 and the functional coating 4, and is composed of a diamond-like carbon structure with a thickness of 0.5 to 2 μm. The functional coating 4 is made of graphite material doped with boron and has a thickness of 3 to 30 μm. The connection between the layers is close and has a clear process sequence to ensure the overall performance of the electrode.

[0036] In the actual preparation process, the base layer 1 is first pretreated to form a roughened layer 2. A nickel plate with a thickness of 0.5 mm is used as an example for the base layer 1. It is immersed in an 8% hydrochloric acid solution and ultrasonically treated at 70°C for 20 minutes to remove the surface oxide layer and oil stains. Subsequently, the nickel plate is ultrasonically degreased with ethanol and rinsed with deionized water until it is neutral. The cleaned nickel plate is then roughened by sandblasting, using Al2O3 sand or SiO2 quartz sand with a particle size of 100 μm and an air pressure of 0.5 MPa. After the above treatment, the surface roughness Ra of the nickel plate reaches 3.2 μm, which meets the requirements for subsequent coating adhesion. The formation of the roughened layer 2 not only enhances the bonding strength between the base layer 1 and the transition coating 3, but also provides a good foundation for subsequent flow channel forming.

[0037] Channel forming is one of the important steps of the present invention. The channel type is selected and processed according to the characteristics of the electrolyte. For example, in low viscosity systems, a straight channel design is used with a channel width of 3mm and a depth of 2mm; in high viscosity systems, a serpentine channel design is used with a bending angle of 90° and a channel spacing of 5mm; in cases where three-dimensional mass transfer is required, a porous array channel design is used, such as Figure 2As shown, the pore diameter is 1 mm and the pore spacing is 3 mm. The porous array flow channels are formed by a stamping process with a punch temperature of 60°C, a pressure of 10 MPa, and a holding time of 20 seconds. During the stamping process, the flow channel edges are ensured to be smooth, with dimensional accuracy controlled within ±0.05 mm. The flow channel design optimizes the electrolyte flow path, reduces mass transfer resistance, and thus improves the electrode reaction efficiency.

[0038] The deposition of the transition coating 3 is achieved through a low-pressure chemical vapor deposition process. The pretreated substrate layer 1 is placed in a reaction chamber, and a mixture of CH4 and H2 is introduced with a volume ratio of 1:7 and a gas flow rate of 100 sccm and 700 sccm, respectively. The reaction chamber temperature is set to 750°C, the pressure is 50 Pa, and the deposition time is 2 hours. Under these conditions, a diamond-like carbon (DLC) transition layer 3 with a thickness of 1 μm is generated on the surface of the substrate layer 1. The formation of the DLC transition layer 3 not only improves the interfacial bonding strength between the substrate layer 1 and the functional coating 4, but also acts as a stress buffer, avoiding the problem of coating cracking caused by differences in thermal expansion coefficients.

[0039] The functional coating 4 is prepared by low-pressure chemical vapor deposition. On the basis of generating the transition coating 3, a mixed gas of CH4 and H2 is continued to be introduced into the reaction chamber, and the volume ratio is still 1:7, and 100ppm trimethylboron (TMB) is introduced as a doping source. The temperature of the reaction chamber is maintained at 750°C, the pressure is 50Pa, and the deposition time is 2 hours. Finally, a boron-doped carbon / graphite carbon coating with a thickness of 10μm is formed on the surface of the base layer 1, namely the functional coating 4. The boron content in the functional coating 4 is 2%, and the conductivity and catalytic activity of the coating are significantly improved by doping with boron. In addition, the microstructure of the functional coating 4 is uniform and dense, which further enhances the corrosion resistance of the electrode.

[0040] In order to further optimize the electrode performance, a post-processing step is required. The coated electrode is annealed in an atmosphere of 95% N2 + 5% H2 at a temperature of 400°C for 1.5 hours. During the annealing process, the internal stress is effectively eliminated, the degree of graphitization of the coating is significantly improved, and the Raman spectrum test shows that the G / D peak intensity ratio reaches 2.5. In addition, a PTFE solution (solid content 5%) can be optionally coated for hydrophobic treatment to make the electrode surface contact angle reach 100°. The hydrophobic treatment reduces the retention of the electrolyte on the electrode surface, reduces the probability of side reactions, and thus extends the service life of the electrode.

[0041] The electrode of the present invention is suitable for zero-gap electrolytic cell design, and its operating principle is as follows: the electrolyte enters the electrode surface through the flow channel and undergoes an electrochemical reaction with the functional coating 4. The doped boron element in the functional coating 4 significantly improves the catalytic activity of the electrode, allowing the reactants to be efficiently converted on the electrode surface. At the same time, the optimized flow channel structure ensures the uniform distribution and rapid renewal of the electrolyte, thereby improving the mass transfer efficiency. For example, in a certain organic electrosynthesis reaction, the electrolyte is a low-viscosity system, and a straight-through flow channel design is adopted with a flow rate of 6 mL / s. Under the condition that the electrolytic cell voltage is 2.8 V, the current efficiency reaches 96%, which is more than 10% higher than that of traditional graphite electrodes. In addition, since the thickness of the base layer 1 is only 0.5 mm, the overall weight of the electrode is light, which is convenient for installation and maintenance.

[0042] The preparation method of the present invention also includes the flexible adjustment of various process parameters to meet the needs of different application scenarios. For example, in a high viscosity system, a serpentine flow channel design can be adopted with a bending angle of 120° and a flow channel spacing of 6 mm. In this case, the base layer 1 is a titanium plate with a thickness of 1.2 mm, and the roughened layer 2 is formed by an electrochemical etching process using a 1 mol / L H2SO4 solution and a current density of 8 mA / cm 2 . The deposition conditions of the transition coating 3 and the functional coating 4 remain unchanged, but the thickness of the functional coating 4 can be increased to 20μm to further improve the corrosion resistance of the electrode. In another application scenario, a porous array flow channel design is adopted with a pore diameter of 0.8mm and a pore spacing of 4mm, which is suitable for reaction systems with high three-dimensional mass transfer requirements. At this time, the base layer 1 is made of iron plate with a thickness of 0.8mm, and the roughening layer 2 is formed by a sandblasting process using Al2O3 sand or SiO2 quartz sand with a particle size of 80μm, and the air pressure is set to 0.4MPa.

[0043] The electrode preparation method of the present invention is as follows Figure 3 As shown in the figure, the complete steps from pretreatment of the substrate layer 1 to post-treatment optimization are clearly visible. Each step is strictly controlled to ensure stable and reliable performance of the electrode. For example, in the pretreatment stage of the substrate layer 1, parameters such as time, temperature and pressure of chemical cleaning and mechanical treatment must be precisely controlled to ensure that the surface roughness of the roughened layer 2 meets the requirements. In the flow channel forming stage, the temperature, pressure and holding time of the stamping process directly affect the dimensional accuracy and surface quality of the flow channel. In the deposition stage of the transition coating 3 and the functional coating 4, the optimization of parameters such as gas flow, reaction temperature and pressure determines the thickness and composition distribution of the coating. In the post-treatment stage, the choice of annealing temperature and time has an important influence on the degree of graphitization and hydrophobicity of the coating.

[0044] The electrode of the present invention has significant technical advantages. The thickness of its base layer 1 can be as low as 0.1mm, and the flow channel structure is flexible and adjustable to meet the mass transfer requirements of different reaction systems. For example, in one experiment, a titanium plate with a thickness of 0.3mm was used as the base layer 1, and the roughened layer 2 was formed by electrochemical etching using a 1mol / L H2SO4 solution and a current density of 6mA / cm 2 The deposition conditions of the transition coating 3 and the functional coating 4 remained unchanged, but the thickness of the functional coating 4 was increased to 15 μm. Under the condition of an electrolytic cell voltage of 2.9 V, the current efficiency reached 97%, and the electrode life exceeded 600 hours, which is more than twice that of traditional graphite electrodes. In addition, the cost of the electrode of the present invention is only 3% of that of precious metal electrodes, which has significant economic advantages.

[0045] The electrode of the present invention can also be applied to a variety of organic electrosynthesis reaction systems. For example, in a certain high viscosity system, a serpentine flow channel design is adopted with a bending angle of 100° and a flow channel spacing of 7 mm. The base layer 1 is a nickel plate with a thickness of 1.0 mm, and the roughening layer 2 is formed by a sandblasting process using Al2O3 sand or SiO2 quartz sand with a particle size of 120 μm, and the air pressure is set to 0.6 MPa. The deposition conditions of the transition coating 3 and the functional coating 4 remain unchanged, but the thickness of the functional coating 4 is increased to 25 μm. Under the condition of an electrolytic cell voltage of 3.0 V, the current efficiency reaches 95% and the electrode life exceeds 550 hours. In addition, after the hydrophobic treatment, the surface contact angle of the electrode of the present invention reaches 110°, which significantly reduces the retention of the electrolyte, thereby reducing the probability of side reactions.

[0046] The electrode preparation method of the present invention is highly flexible and operable, and parameters can be adjusted according to specific application scenarios. For example, in a low-viscosity system, a straight-through flow channel design is adopted, with a flow channel width of 4 mm and a depth of 2.5 mm. The base layer 1 is made of iron plate with a thickness of 0.6 mm, and the roughening layer 2 is formed by a sandblasting process using Al2O3 sand or SiO2 quartz sand with a particle size of 60 μm, and the air pressure is set to 0.3 MPa. The deposition conditions of the transition coating 3 and the functional coating 4 remain unchanged, but the thickness of the functional coating 4 is reduced to 5 μm. Under the condition that the electrolytic cell voltage is 2.7 V, the current efficiency reaches 98% and the electrode life exceeds 500 hours. In addition, after the hydrophobic treatment, the surface contact angle of the electrode of the present invention reaches 95°, which significantly reduces the retention of the electrolyte, thereby extending the service life of the electrode.

[0047] In order to better enable relevant personnel in this technical field to fully understand and implement the present invention, the operating principle and implementation steps of the present invention are further supplemented below in combination with specific application scenarios.

[0048] In a certain organic electrosynthesis system, the electrolyte is a low-viscosity system, and a straight-through flow channel design is employed, with a channel width of 3 mm and a depth of 2 mm. A 0.5 mm thick nickel plate is used as the base layer 1. The nickel plate is first immersed in an 8% hydrochloric acid solution and ultrasonically treated at 70°C for 20 minutes to remove the surface oxide layer and oil contamination. It is then ultrasonically degreased with ethanol and rinsed with deionized water until neutral. The nickel plate is then roughened using a sandblasting process, using 100 μm Al2O3 sand or SiO2 quartz sand at a pressure of 0.5 MPa. After this treatment, the nickel plate achieves a surface roughness Ra of 3.2 μm, meeting the adhesion requirements for subsequent coatings. The formation of the roughened layer 2 not only enhances the bond strength between the base layer 1 and the transition coating 3 but also provides a good foundation for subsequent flow channel formation.

[0049] During the runner forming stage, a straight-through runner design was selected based on the electrolyte's characteristics, with a width of 3mm and a depth of 2mm. The runners were processed using a stamping process, with a punch temperature of 60°C, a pressure of 10 MPa, and a hold time of 20 seconds. The stamping process ensured smooth runner edges, with dimensional accuracy controlled within ±0.05mm. This optimized runner structure reduces electrolyte flow resistance, thereby improving mass transfer efficiency.

[0050] The deposition of the transition coating 3 is achieved through a low-pressure chemical vapor deposition process. The pretreated substrate layer 1 is placed in a reaction chamber and a mixture of CH4 and H2 is introduced at a volume ratio of 1:7, with gas flow rates of 100 sccm and 700 sccm, respectively. The reaction chamber temperature is set to 750°C, the pressure is 50 Pa, and the deposition time is 2 hours. Under these conditions, a diamond-like carbon (DLC) transition layer 3 with a thickness of 1 μm is generated on the surface of the substrate layer 1. The formation of the transition coating 3 improves the interfacial bonding strength between the substrate layer 1 and the functional coating 4, while also buffering the stress concentration problem caused by the difference in thermal expansion coefficient.

[0051] The functional coating 4 is prepared by low-pressure chemical vapor deposition. On the basis of generating the transition coating 3, a mixed gas of CH4 and H2 is continued to be introduced into the reaction chamber, and the volume ratio is still 1:7. At the same time, 100ppm trimethylboron (TMB) is introduced as a doping source. The temperature of the reaction chamber is maintained at 750°C, the pressure is 50Pa, and the deposition time is 2 hours. Finally, a boron-doped carbon / graphite carbon coating with a thickness of 10μm is formed on the surface of the base layer 1, namely the functional coating 4. The boron content in the functional coating 4 is 2%. By doping with boron, the conductivity and catalytic activity of the coating are significantly improved.

[0052] The post-processing stage includes annealing and hydrophobic treatment. The coated electrode is annealed in a 95% N2 + 5% H2 atmosphere at a temperature of 400°C for 1.5 hours. During the annealing process, the internal stress is effectively eliminated, the degree of graphitization of the coating is significantly improved, and Raman spectroscopy tests show that the G / D peak intensity ratio reaches 2.5. In addition, a PTFE solution with a solid content of 5% is coated for hydrophobic treatment, so that the contact angle of the electrode surface reaches 100°. The hydrophobic treatment reduces the retention of electrolyte on the electrode surface and reduces the probability of side reactions.

[0053] During actual operation, the electrolyte is evenly distributed across the electrode surface through the straight flow channels, where it undergoes an electrochemical reaction with the functional coating 4. The boron doping in the functional coating 4 significantly enhances the electrode's catalytic activity, enabling efficient conversion of reactants on the electrode surface. The optimized flow channel structure ensures rapid electrolyte turnover, thereby improving mass transfer efficiency. At an electrolytic cell voltage of 2.8V, the current efficiency reaches 96%, an improvement of over 10% compared to conventional graphite electrodes.

[0054] In another application scenario of a high-viscosity system, a serpentine flow channel design is adopted with a bending angle of 100° and a flow channel spacing of 7mm. The base layer 1 is a nickel plate with a thickness of 1.0mm, and the roughening layer 2 is formed by a sandblasting process using Al2O3 sand or SiO2 quartz sand with a particle size of 120μm, and the air pressure is set to 0.6MPa. The deposition conditions of the transition coating 3 and the functional coating 4 remain unchanged, but the thickness of the functional coating 4 is increased to 25μm. Under the condition of an electrolytic cell voltage of 3.0V, the current efficiency reaches 95% and the electrode life exceeds 550 hours. In addition, after the hydrophobic treatment, the surface contact angle of the electrode reaches 110°, which significantly reduces the retention of the electrolyte, thereby reducing the probability of side reactions.

[0055] In a reaction system requiring three-dimensional mass transfer, a porous array flow channel design is adopted with a pore size of 0.8 mm and a pore spacing of 4 mm. The base layer 1 is made of an iron plate with a thickness of 0.8 mm. The roughening layer 2 is formed by a sandblasting process using Al2O2 sand or SiO2 quartz sand with a particle size of 80 μm, and the air pressure is set to 0.4 MPa. The thickness of the functional coating 4 is 15 μm. Under the condition of an electrolytic cell voltage of 2.9 V, the current efficiency reaches 97% and the electrode life exceeds 600 hours. After hydrophobic treatment, the surface contact angle reaches 105°, further extending the service life of the electrode.

[0056] The electrode preparation method of the present invention is highly flexible and can be adjusted according to the specific application scenario. For example, in a low viscosity system, a straight-through flow channel design is adopted, and the flow channel width is 4 mm and the depth is 2.5 mm. The base layer 1 is an iron plate with a thickness of 0.6 mm, and the roughening layer 2 is formed by a sandblasting process, using Al2O2 sand or SiO2 quartz sand with a particle size of 60 μm, and the air pressure is set to 0.3 MPa. The thickness of the functional coating 4 is reduced to 5 μm. Under the condition of an electrolytic cell voltage of 2.7 V, the current efficiency reaches 98% and the electrode life exceeds 500 hours. After hydrophobic treatment, the surface contact angle reaches 95°, which significantly reduces the retention of the electrolyte, thereby extending the service life of the electrode.

[0057] The electrode of this invention is suitable for zero-gap electrolytic cell designs. Its base layer (1) thickness can be as low as 0.1 mm, and its flow channel structure is flexible and adjustable to meet the mass transfer requirements of different reaction systems. By optimizing the base layer material, roughening treatment, flow channel design, and coating deposition process, the overall performance of the electrode is significantly improved.

[0058] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions based on the principles of the present invention are within the scope of protection of the present invention. It should be noted that improvements and modifications that do not depart from the principles of the present invention are within the scope of protection of the present invention.

Claims

1. A non-precious metal-based graphite electrode suitable for organic electrosynthesis, characterized in that: The electrode comprises, from bottom to top, a base layer (1), a roughening layer (2), a transition coating (3) and a functional coating (4); the base layer (1) is made of nickel, iron, titanium or an alloy thereof, and has a thickness of 0.1 to 1.5 mm; the surface roughness Ra of the roughening layer (2) is 1.6 to 6.3 μm; the transition coating (3) is a diamond-like carbon structure, and has a thickness of 0.5 to 2 μm; and the functional coating (4) is made of a graphite material doped with boron, and has a thickness of 3 to 30 μm.

2. The non-noble metal-based graphite electrode suitable for organic electrosynthesis according to claim 1, characterized in that: The base layer (1) is subjected to chemical cleaning and mechanical treatment to form a roughened layer (2). The chemical cleaning adopts a 5% to 10% hydrochloric acid solution and ultrasonic treatment at 60 degrees Celsius to 80 degrees Celsius for 10 minutes to 30 minutes. The mechanical treatment is sandblasting or electrochemical etching process.

3. The non-noble metal-based graphite electrode suitable for organic electrosynthesis according to claim 2, characterized in that: The sandblasting process uses Al2O3 sand or SiO2 quartz sand with a particle size of 50 microns to 150 microns, and an air pressure of 0.3 MPa to 0.6 MPa. The electrochemical etching process uses 1 mol / L H2SO4 solution, and a current density of 5 mA / cm2 to 10 mA / cm2.

4. The non-noble metal-based graphite electrode suitable for organic electrosynthesis according to any one of claims 1 to 3, characterized in that: The base layer (1) is provided with a flow channel structure, and the flow channel types include straight flow channels, serpentine flow channels or porous array flow channels (5). The width of the straight flow channel is 2 mm to 5 mm, and the depth is 1 mm to 3 mm. The bending angle of the serpentine flow channel is 60 degrees to 120 degrees, and the flow channel spacing is 2 mm to 8 mm. The pore diameter of the porous array flow channel (5) is 0.5 mm to 2 mm, and the pore spacing is 2 mm to 5 mm.

5. The non-noble metal-based graphite electrode suitable for organic electrosynthesis according to claim 4, characterized in that: The porous array flow channel (5) is formed by a stamping process, with a punch temperature of 50 degrees Celsius to 80 degrees Celsius, a pressure of 5 MPa to 20 MPa, and a holding time of 5 seconds to 30 seconds.

6. The non-noble metal-based graphite electrode suitable for organic electrosynthesis according to any one of claims 1 to 5, characterized in that: The transition coating (3) is prepared by a low-pressure chemical vapor deposition method, the reaction gas is a mixed gas of CH4 and H2, the volume ratio is 1:5 to 1:10, the reaction temperature is 600 degrees Celsius to 900 degrees Celsius, the pressure is 10 Pa to 100 Pa, and the deposition time is 1 hour to 3 hours.

7. The non-noble metal-based graphite electrode suitable for organic electrosynthesis according to any one of claims 1 to 6, characterized in that: The functional coating (4) is prepared by low-pressure chemical vapor deposition or gas phase physical deposition, wherein 50 ppm to 200 ppm of trimethylboron is introduced as a doping source in the low-pressure chemical vapor deposition, a graphite target or a B4C target is used in the gas phase physical deposition, the argon gas pressure is 0.1 Pa to 1 Pa, and the power is 100 W to 500 W.

8. A method for preparing a non-noble metal-based graphite electrode suitable for organic electrosynthesis, characterized in that: The method comprises the following steps: Step 1: Select nickel, iron, titanium or their alloy plates as the base layer (1), control the thickness within the range of 0.1 mm to 1.5 mm, and perform chemical cleaning and mechanical treatment to form a roughened layer (2); Step 2: Select the flow channel type according to the characteristics of the electrolyte and perform molding processing; Step 3: During the deposition of the transition coating (3), the pretreated base layer (1) is placed in a reaction chamber, and a mixed gas of CH4 and H2 is introduced to deposit and form a diamond-like carbon structure; Step 4: During the deposition of the functional coating (4), a boron-doped graphite coating is formed by low-pressure chemical vapor deposition or vapor phase physical deposition; Step 5: Post-processing optimization of the coated electrode, including annealing and optional hydrophobic treatment.

9. The method for preparing a non-noble metal-based graphite electrode suitable for organic electrosynthesis according to claim 8, characterized in that: The annealing treatment is performed in an atmosphere of 95% N2+5% H2 at a temperature of 300 to 500 degrees Celsius for a time of 1 to 2 hours.

10. The method for preparing a non-noble metal-based graphite electrode suitable for organic electrosynthesis according to claim 8 or 9, characterized in that: The hydrophobic treatment is achieved by coating a PTFE solution, so that the contact angle of the electrode surface reaches 90 degrees to 120 degrees.

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