Preparation method of BDD electrode

Abstract

The invention discloses a BDD electrode material and a preparation method thereof. The preparation method comprises the following core steps: pretreating the surface of a porous titanium substrate; depositing a nanoscale TiN film layer on the surface of the pretreated porous titanium substrate in advance; depositing a layer of single-walled carbon nanotube network on the TiN thin film layer by using an electrophoretic deposition method; growing a highly-doped BDD layer on the single-walled carbon nanotube network by adopting a plasma enhanced chemical vapor deposition technology; repeating the two steps to form a multi-layer SWCNT / BDD composite structure, and controlling the thickness of the multi-layer SWCNT / BDD composite structure to be 1-50 microns; and finally, depositing a low-doped BDD active layer with the thickness of 1-5 microns by adopting a hot filament chemical vapor deposition (HFCVD) technology. According to the pulse laser assisted preparation process provided by the invention, the femtosecond laser pulse is introduced to replace traditional plasma treatment, so that the process flow is simplified, and the efficiency is improved; according to the technology, the process is simplified, the quality of the TiN film is improved through accurate energy input, and a new way is opened up for further improving the performance of the BDD electrode.

Description

Technical Field

[0001] The invention relates to the technical field of electrode materials and organic electrochemical synthesis, and in particular to a preparation method of a BDD electrode. Background Art

[0002] Boron-doped diamond (BDD) electrodes are widely used due to their inertness to poisoning across a wide potential window and their high stability at high current densities. For example, in a 1M H₂SO₄ solution, BDD electrodes can be overpolarized at a current density of 1 A / cm² for 250 hours without exhibiting etching. BDD electrodes are reportedly generally more corrosion-resistant than Pt electrodes under Kolbe electrolysis conditions, extending their service life and increasing electrolysis operating time.

[0003] Kolbe electrolysis on boron-doped diamond (BDD) electrodes has been relatively understudied. Typically, the electrooxidation process is carried out in electrolytes containing methanol, sulfate, or perchlorate. For example, there are reports of the complete oxidation of formic acid to carbon dioxide via direct electron transfer. Furthermore, a single BDD layer structure struggles to achieve both high conductivity and good electrochemical performance.

[0004] This invention provides a BBD electrode. By introducing a TiN thin film layer and a single-walled carbon nanotube network into the BDD, and low-doping the BDD active layer on the BDD surface, the reaction mechanism can be regulated to form Kolbe products. Compared with other substrates (graphite, nickel foam, and fluorine-doped tin oxide), the BDD electrode prepared by this invention is an ideal electrode material. The invention proposes incorporating a carbon nanotube network into the multilayer BDD electrode structure to significantly improve the electrode's conductivity. Summary of the Invention

[0005] To solve the problems raised in the above background technology, the present invention discloses a BDD electrode material and a preparation method thereof. First, the surface of a porous titanium substrate is pretreated; then a layer of nanoscale titanium nitride (TiN) thin film is pre-deposited on the pretreated surface of the porous titanium substrate; on the TiN thin film layer, a layer of single-walled carbon nanotube network is deposited using electrophoretic deposition; plasma-enhanced chemical vapor deposition (PECVD) technology is used to grow a highly doped BDD layer on the single-walled carbon nanotube network; the above two steps are repeated to form a multilayer SWCNT / BDD composite structure with a thickness controlled at 1-50 μm; finally, a low-doped BDD active layer of 1-5 μm is deposited using hot filament chemical vapor deposition (HFCVD) technology.

[0006] The pulsed laser-assisted fabrication process proposed in this paper replaces traditional plasma treatment with femtosecond laser pulses, simplifying the process and improving efficiency. This innovative process not only simplifies the process but also improves the quality of TiN films through precise energy input, opening up new avenues for further improving the performance of BDD electrodes.

[0007] By introducing a TiN thin film layer into BDD, the electronic structure of the electrode surface can be further optimized, thereby improving its electrocatalytic activity. The multilayer SWCNT / BDD composite structure can increase the equivalent conductivity of the BDD electrode to 2.0-2.5×10 5 S / cm. Furthermore, the presence of the SWCNT network enhances the mechanical strength of the electrode and improves its fatigue resistance. Finally, when preparing the BDD active layer, precise control of the SWCNT deposition voltage (50-100 V), the methane / B2H6 ratio (1:1000-1:2000) during PECVD, and the growth temperature (800-850°C) allows for a good integration of the SWCNTs with the BDD lattice.

[0008] To achieve the above object, the present invention provides the following technical solutions: The present invention provides a BDD electrode material consisting of a six-level functionalized structure, including: Pre-treated porous titanium substrate: through electrochemical anodization activation treatment method, this method uses electrochemical process to achieve surface cleaning and activation, while improving the conductivity and catalytic activity of the substrate by forming a special oxide layer structure; TiN thin film: In an atomic layer deposition (ALD) chamber, pulsed lasers are used to deposit a 5-10 nm thick TiN thin film. Femtosecond laser pulses generate localized high temperatures (>1000°C) within nanoseconds, promoting TiN crystallization and densification while preventing overheating of the substrate. Single-walled carbon nanotube network layer: Using electrophoretic deposition method, the thickness of the single-walled carbon nanotube network layer deposited on the TiN film layer is controlled to be 50-100 nm, and the network density is 1-2×10 10 tubes / cm 2 ; Highly doped BDD layer: Plasma enhanced chemical vapor deposition (PECVD) technology is used to grow a highly doped BDD layer on the single-walled carbon nanotube network (SWCNT) layer, and the doping concentration is maintained at 1.5-2×10 21 cm -3 , thickness of 1-1.5 μm; Multilayer SWCNT / BDD composite structure: Repeated steps of depositing SWCNT layers and preparing highly doped BDD layers form a multilayer SWCNT / BDD composite structure with a thickness controlled between 1 and 50 μm. The presence of the SWCNT network can enhance the mechanical strength of the electrode and improve its fatigue resistance.

[0009] BDD active layer: A 1-5μm low-doped BDD active layer is deposited using hot filament chemical vapor deposition (HFCVD). By precisely controlling the SWCNT deposition voltage, the methane / B2H6 ratio of PECVD, and the growth temperature, a good bond between the SWCNT and the BDD lattice can be achieved.

[0010] The present invention also provides a method for preparing a BDD electrode material, comprising the following steps: S01. Pretreatment of porous titanium substrate: The porous titanium substrate is used as anode, the inert electrode graphite is used as cathode, and the electrolyte is 0.5 M Na2SO4 solution. Electrochemical treatment is carried out at room temperature (20-25°C) and a constant current density (100-200 A / m 2 The treatment time is 1-2 hours. By controlling the electrolysis conditions, an oxide layer with a specific morphology and composition is formed on the titanium surface. After treatment, a low-temperature annealing (350-400°C, 0.5-1 hour) is performed to stabilize the oxide layer structure.

[0011] S02. Preparation of TiN thin film layer: The pretreated porous titanium substrate is placed in an atomic layer deposition reaction chamber, TiCl4 is used as a Ti precursor, NH3 is used as a N precursor, and the deposition temperature is 250-300°C. Under the conditions of femtosecond laser pulses, NH3 reacts with TiCl4 adsorbed on the surface of the substrate to form a 5-10 nm TiN thin film layer. In order to achieve the required film thickness, the above atomic layer deposition cycle is repeated multiple times. Each atomic layer deposition cycle includes: TiCl4 pulse (0.1 s) - purification (3 s) - NH3 pulse (1 s) - laser irradiation (0.5 s) - purification (3 s). The laser energy density is controlled at 50-100 mJ / cm 2 , uniform irradiation is ensured by a scanning galvanometer system.

[0012] S03. Deposition of single-walled carbon nanotubes: placing the porous titanium substrate obtained in step S02 in an electrophoresis tank containing 0.1-1 mg / mL single-walled carbon nanotubes and 1%-5% sodium dodecyl sulfate dispersion, and using a power of 200W-400W for ultrasonic treatment for 10-30 minutes; using the ultrasonically treated porous titanium substrate as a cathode and a platinum electrode as an anode, immersing them in a dispersion containing 0.1-1 mg / mL single-walled carbon nanotubes and 1%-5% sodium dodecyl sulfate, with the distance between the anode and the cathode maintained at 1-5 cm, applying a DC voltage of 20-50 V, and controlling the deposition time to be 5-15 minutes. After the deposition is completed, the porous titanium substrate is washed with deionized water, and then dried at 60-80°C for 10-20 minutes, and heat-treated at 300-500°C for 1-2 hours to remove the surfactant and enhance the adhesion, thereby completing the deposition of the SWCNT network and obtaining a SWCNT network porous titanium substrate.

[0013] S04, preparation of highly doped BDD layer: dry the SWCNT network porous titanium substrate obtained in step S03 and place it in the HFCVD chamber for deposition. Close the chamber door, start the vacuum pump, and evacuate the chamber to 10 -4 The chamber is evacuated at a pressure of approximately 100 Pa, and the vacuum time is 30-60 minutes to ensure that no impurities in the chamber interfere with the deposition process. After the vacuum reaches the set value, a doping boron source, a carbon source, and a carrier gas are introduced at a precisely controlled gas flow ratio using a gas flow controller. The RF power supply is turned on to generate a highly active plasma, promoting the decomposition and deposition of the reactant gases. During the deposition process, the chamber temperature is controlled between 400-700°C, the deposition pressure is maintained between 1-5 kPa, and the deposition time is set between 1-5 hours to grow a highly doped BDD layer of a certain thickness. The deposition rate is expected to be 10-30 nm / min. During the deposition process, the plasma emission spectrum is monitored in real time using an in-situ monitoring system. After deposition is complete, the RF power supply and gas flow controller are turned off, and the chamber is allowed to cool naturally to room temperature for approximately 30 minutes. After cooling, the chamber door is opened and the deposited porous titanium substrate is carefully removed. The substrate is then cleaned in a 40 kHz ultrasonic cleaning tank with deionized water for 5 minutes to remove residual reactants and impurities on the surface. After cleaning, the porous titanium substrate was dried using nitrogen gas.

[0014] S05. Preparation of a multilayer SWCNT / BDD composite structure: Repeat steps S03 and S04 to form a multilayer SWCNT / BDD composite structure with a thickness controlled within a range of 1-50 μm.

[0015] S06, preparation of BDD active layer: the multi-layer SWCNT / BDD composite structure substrate obtained in step S05 is dried and placed in the HFCVD chamber for deposition. Close the chamber door, start the vacuum pump, and evacuate the chamber to 10 -4The chamber is evacuated for 30-60 minutes to ensure that no impurities interfere with the deposition process. After the vacuum reaches the set value, the reactant gases are introduced at a precisely controlled gas flow ratio using a gas flow controller. After the vacuum reaches the set value, the reactant gases are precisely introduced using a gas flow controller, and the RF power supply is turned on to generate a highly active plasma, promoting the decomposition and deposition of the reactant gases. During the deposition process, the chamber temperature is controlled at 800-850°C, the deposition pressure is maintained at 1-5 kPa, and the deposition time is set to 1-5 hours to grow a low-doped BDD layer. The deposition rate is expected to be 5-20 nm / min. During the deposition process, the plasma emission spectrum is monitored in real time using an in-situ monitoring system. After deposition is complete, the RF power supply and gas flow controller are turned off, and the chamber is allowed to cool naturally to room temperature for approximately 30 minutes. After cooling, the chamber door is opened and the deposited BDD electrode is carefully removed. The substrate is cleaned in an ultrasonic bath with deionized water for 10 minutes at a frequency of 25 kHz to remove residual reactants and impurities on the surface. After cleaning, use nitrogen to blow dry the BBD electrode.

[0016] Furthermore, in step S02, the atomic layer deposition adopts an integrated femtosecond laser system, and the femtosecond laser pulse conditions include: wavelength 800 nm, pulse width 100 fs, and repetition frequency 1 kHz.

[0017] Furthermore, in step S04, the doping boron source is an ethanol solution of boron trioxide, which is brought into the chamber by a carrier gas. The carbon source is methane, the carrier gas is hydrogen, and the gas flow ratio of boron trioxide, methane, and hydrogen is 4000-5000:1:10.

[0018] Preferably, the methane (CH4) flow rate is set to 30 sccm and the hydrogen flow rate is set to 300 sccm.

[0019] Furthermore, in step S06, the reaction gases are methane and B2H6, and the gas flow ratio of methane to B2H6 is 1:1000-1:2000.

[0020] Furthermore, in step S04 and step S06, the RF power frequency is set to 13.56 MHz, the power is adjusted to 400 W, and the power density is approximately 0.3 W / cm².

[0021] Compared with the prior art, the present invention has the following beneficial effects: The BDD electrode material prepared by the present invention consists of a six-level functionalized structure: a pre-treated porous titanium substrate is used as a supporting carrier, and by introducing a TiN thin film layer into the BDD, the electronic structure of the electrode surface can be further optimized and its electrocatalytic activity can be improved; the present invention proposes a gradient-doped BDD electrode preparation process, which realizes the synergistic optimization of the electrode conductivity and electrochemical performance by dynamically regulating the doping concentration during the growth process. A layer of highly doped (B / C ratio of about 8000-10000 ppm) BDD film (thickness of 1-1.5 μm) is first grown on the surface of the single-walled carbon nanotube substrate to provide a good conductive channel; the doping concentration is gradually reduced, and the B / C ratio of the final surface layer is controlled at 2000-4000 ppm to ensure excellent electrochemical performance; this method can increase the bulk conductivity of the BDD electrode by 5-10 times, while maintaining a wide potential window (>3 V) and low background current (<10 μA / cm 2 ). This gradient doping structure not only ensures the overall conductivity of the electrode, but also maintains the excellent electrochemical properties of the surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the SEM image of the BDD electrode prepared in Example 1; Figure 2 Schematic diagram of the electrochemical performance test of the BDD electrode prepared in Example 2. DETAILED DESCRIPTION

[0023] 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.

[0024] Contains 1 mg / mL single-walled carbon nanotubes and 1% sodium dodecyl sulfate dispersion. Preparation process: Step A Material preparation: (1) Single-walled carbon nanotubes (SWCNT): Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., conductivity > 2000 s / cm, specific surface area > 1075 m 2 / g, content>95%. (2) Sodium lauryl sulfate: chemically pure, Nanjing Chemical Reagent Co., Ltd., content>99%. (3) Deionized water: used as solvent.

[0025] Step B Preparation process: (1) Prepare 1 mg / mL single-walled carbon nanotube dispersion: Use an electronic balance to accurately weigh 100 mg of single-walled carbon nanotube powder. Add the weighed SWCNTs to 100 mL of deionized water. Use an ultrasonic disperser to sonicate the SWCNTs for 1 hour to ensure that the SWCNTs are fully dispersed to obtain an initial 1 mg / mL single-walled carbon nanotube dispersion. (2) Add surfactant. To improve the dispersibility of SWCNTs, add an appropriate amount of sodium dodecyl sulfate as a surfactant. Add 1 g of sodium dodecyl sulfate (i.e., a concentration of 1%) and stir on a magnetic stirrer until the sodium dodecyl sulfate is completely dissolved. It can be heated to 45°C to accelerate dissolution.

[0026] Step C: Mixed solution: (1) The prepared mixed solution was ultrasonically treated again using an ultrasonic disperser to ensure that the 1 mg / mL SWCNT and the sodium dodecyl sulfate solution were evenly dispersed. The total ultrasonic time was 60 minutes. The ultrasonication was performed intermittently during the process to prevent local overheating. The ultrasonication was continued for 10 minutes, and then paused for 5 minutes. This process was repeated until the total ultrasonication time was completed. A dispersion containing 1 mg / mL SWCNT and 1% sodium dodecyl sulfate was obtained.

[0027] Doping boron source, preparation process: Step A: Material preparation: (1) Boron trioxide (B2O3): chemically pure, Nanjing Chemical Reagent Co., Ltd., content >99%. (2) Anhydrous ethanol: analytically pure, Nanjing Chemical Reagent Co., Ltd., content >99.7%.

[0028] Step B Preparation: Accurately weigh 6.962 g of boron trioxide powder. Add the weighed boron trioxide powder to 50 g of anhydrous ethanol, initially adding a small amount of ethanol to fully moisten the powder. Stir the solution at room temperature. Place the solution in a heating device and slowly heat it to 70°C. Maintain this temperature and stir for 3 hours to ensure complete dissolution of the boron trioxide. Transfer the dissolved solution to a 100 mL volumetric flask and dilute to 100 mL with anhydrous ethanol for a concentration of 1 mol / L. Example 1

[0029] (1) Pretreatment of porous titanium substrate: insert a 2*2*0.2cm porous pure titanium plate anode and a 2*2*0.2cm graphite cathode into the electrolytic reactor, and control the distance between the anode and cathode to be 10mm. Add a 0.5M Na2SO4 solution into the electrolytic reactor and start stirring. During the electrochemical treatment, control the electrochemical treatment temperature to 25℃ and the electrochemical treatment current density to 200A / m². The electrochemical treatment lasts for 2h. Subsequently, the treated porous titanium substrate is placed in a muffle furnace for low-temperature annealing treatment at 400℃ for 30min to stabilize the oxide layer structure, thereby obtaining a pretreated porous titanium substrate.

[0030] (2) Preparation of TiN thin film layer: Place the pretreated porous titanium substrate in the atomic layer deposition reaction chamber, close the chamber door, start the vacuum pump, and evacuate the chamber to 10 -3 The deposition process is maintained at approximately 100 Pa to ensure that no impurities in the reaction chamber interfere with the deposition process. The substrate is slowly heated to 260°C to prevent cracking due to thermal stress. At the beginning of the deposition process, a pulse of TiCl₄, a titanium precursor gas, is introduced. A gas flow controller precisely controls the TiCl₄ flow rate to 20 sccm (standard cubic centimeters per minute) with a pulse duration of 0.1 seconds. Once TiCl₄ forms a monolayer on the substrate surface, the process switches to a purge phase. High-purity argon (≥99.999%) is used as the purge gas at a flow rate of 200 sccm for a purge duration of 3 seconds to remove excess TiCl₄ and reaction byproducts from the reaction chamber. Subsequently, a pulse of NH₃, a nitrogen precursor gas, is introduced. A gas flow controller controls the NH₃ flow rate to 50 sccm with a pulse duration of 1 second. Under the conditions of the femtosecond laser pulse, the NH₃ reacts with the TiCl₄ adsorbed on the substrate surface to form a TiN thin film. The laser energy density is controlled at 100 mJ / cm⁻¹. 2 , and ensure uniform irradiation by scanning the galvanometer system. After the reaction is completed, argon is used to purge the reaction chamber again to remove excess NH3 and reaction by-products. The purge time is 3 seconds. The above steps are a complete deposition cycle. In order to achieve the required film thickness, the above cycle is repeated 5 times. Each atomic layer deposition cycle includes: TiCl4 pulse (0.1 s) - purification (3 s) - NH3 pulse (1 s) - laser irradiation (0.5 s) - purification (3 s). After the deposition is completed, all gas flow controllers are turned off and the pulsed introduction of precursor gas is stopped. Continue to purge the reaction chamber with argon to ensure that the reaction by-products are completely discharged. Subsequently, the substrate is naturally cooled to room temperature for 30 minutes. After cooling is completed, open the reaction chamber and carefully remove the deposited porous titanium substrate.

[0031] The thickness of the TiN film was measured using a professional ellipsometer, which showed a thickness of 8.5 nm.

[0032] Deposition of single-walled carbon nanotubes: The porous titanium substrate obtained in step (2) was placed in an electrophoresis tank containing 1 mg / mL single-walled carbon nanotubes and 1% sodium dodecyl sulfate dispersion, and ultrasonic treatment was performed at a power of 200 W for 10 minutes to ensure uniform dispersion of SWCNTs. The porous titanium substrate was used as the cathode and the platinum electrode was used as the anode. They were immersed in a dispersion containing 1 mg / mL single-walled carbon nanotubes and 1% sodium dodecyl sulfate dispersion. The distance between the anode and the cathode was kept at 1 cm. A DC voltage of 20 V was applied and the deposition time was controlled within 10 minutes. After the deposition was completed, the porous titanium substrate was washed with deionized water to remove the undeposited SWCNTs. Then, it was dried at 80°C for 10 minutes and heat-treated at 500°C for 1 hour to remove the surfactant and enhance adhesion.

[0033] Thickness of the single-walled carbon nanotube network layer: The sample was placed on the sample stage of the atomic force microscope, and the tapping mode was selected to collect multiple step height data at the edge of the film. The thickness of the film was determined by analyzing these step heights, and the thickness was 89nm.

[0034] The SEM image analysis method was used to detect the single-walled carbon nanotube network density, which was 1.95×10 10 tubes / cm², with a network density of 1-2×10 10 tubes / cm 2 .

[0035] (4) Preparation of highly doped BDD layer: Dry the SWCNT network porous titanium substrate obtained in step (3) and place it in the HFCVD chamber for deposition. Close the chamber door, start the vacuum pump, and evacuate the chamber to 10 -4 Pa, and the vacuum time is 30 minutes to ensure that there is no impurity gas in the chamber to interfere with the deposition process. Boron trioxide is dissolved in ethanol as a doping boron source and brought into the chamber by a carrier gas, with methane as the carbon source. After the vacuum reaches the set value, the gas flow controller precisely controls the methane (CH4) flow rate to 30 sccm, the hydrogen flow rate to 300 sccm, and the gas flow ratio CH4:H2:B2O3 to 1:10:4675. Turn on the RF power supply, set the RF power supply frequency to 13.56 MHz, adjust the power to 400 W, and the power density to 0.3 W / cm 2To generate a highly active plasma, the reaction gas decomposition and deposition process was promoted. During the deposition process, the chamber temperature was controlled at 700°C, the deposition pressure was maintained at 5 kPa, and the deposition time was set to 5 hours to grow a highly doped BDD layer of a certain thickness. The deposition rate was expected to be 30 nm / min. During the deposition process, the plasma emission spectrum was monitored in real time using an in-situ monitoring system. After deposition, the RF power supply and gas flow controller were turned off, and the chamber was allowed to cool naturally to room temperature for 30 minutes. After cooling, the chamber door was opened and the deposited porous titanium substrate was carefully removed. The substrate was cleaned in a 40 kHz ultrasonic cleaning bath with deionized water for 5 minutes to remove residual reactants and impurities on the surface. After cleaning, the porous titanium substrate was blown dry with nitrogen. During the deposition process, the thickness of the BDD active layer can be monitored in real time using in-situ monitoring techniques (such as optical interferometry, if the HFCVD system has this capability) to ensure that the thickness is within the range of 1-5 μm, with a thickness of 1.5 μm being the ideal value.

[0036] (5) Preparation of a multilayer SWCNT / BDD composite structure: Repeat steps (3) and (4) 10 times to form a multilayer SWCNT / BDD composite structure. The thickness of the multilayer SWCNT / BDD composite structure was measured using X-ray reflection. The sample was placed in an XRR instrument, and the incident angle and detector position were adjusted to perform X-ray reflection measurement. The measured data were fitted using data analysis software to obtain the total thickness of the multilayer structure, which was 16 μm.

[0037] The capacitance-voltage method is used for detection. This method is based on the capacitance effect of the multilayer SWCNT / BDD composite material. By measuring the capacitance change of the multilayer SWCNT / BDD composite material under different reverse voltages, the doping concentration is calculated. The doping concentration is 1.8×10 21 cm -3 .

[0038] Preparation of BDD active layer: Dry the multilayer SWCNT / BDD composite structure substrate obtained in step (5) and place it in the HFCVD chamber for deposition. Close the chamber door, start the vacuum pump, and evacuate the chamber to 10 -4The chamber was evacuated for 30 minutes to ensure that no impurities in the chamber interfered with the deposition process. After the vacuum reached the setpoint, a gas flow controller precisely controlled the flow rates of methane (CH4) to 10 sccm and B2H6 to 10,000 sccm. After the vacuum reached the setpoint, the reactant gases were precisely introduced through the gas flow controllers, and the RF power supply was turned on to generate a highly active plasma, promoting the decomposition and deposition of the reactant gases. During the deposition process, the chamber temperature was controlled at 850°C, the deposition pressure was maintained at 3 kPa, and the deposition time was set to 2 hours. A low-doped BDD layer was grown. The deposition rate was 10 nm / min, and the plasma emission spectrum was monitored in real time using an in-situ monitoring system. After deposition, the RF power supply and gas flow controller were turned off, and the chamber was allowed to cool naturally to room temperature for 30 minutes. After cooling, the chamber door was opened, and the deposited BDD electrode was carefully removed. The substrate was then cleaned in a deionized water ultrasonic bath at a frequency of 25 kHz for 10 minutes to remove any residual reactants and impurities on the surface. After cleaning, the BBD electrode is dried with nitrogen. During the deposition process, the thickness of the BDD active layer can be monitored in real time using in-situ monitoring techniques (such as optical interferometry, if the HFCVD system has this function) to ensure that the thickness is within the range of 1-50μm, with a thickness of 4.3μm.

[0039] The conductivity of the BDD electrode was tested using the four-probe method. Four probes were placed on the surface of the BDD electrode, current was applied, and the voltage drop was measured to calculate the conductivity of the material. The conductivity was found to be 2.5×10 5 S / cm.

[0040] As shown in Table 1, there is no significant change in Example 1 after 300 hours of electrolysis, indicating that the material has good mechanical strength and fatigue resistance.

[0041] The SEM image of the BDD electrode prepared in Example 1 is as follows: Figure 1As shown in the image, the surface exhibits a distinct three-dimensional porous structure, with pore sizes on the micron scale (the scale indicates a length of 20 µm), and pore sizes ranging from 1 to 5 µm. This three-dimensional porous structure facilitates increased specific surface area. A TiN thin film is deposited on the surface, further improving the electronic structure and enhancing electron mobility, thereby enhancing the electrocatalytic activity of the subsequently deposited BDD layer. The BDD film growth likely retains the porous nature of the titanium substrate, forming a highly adherent, continuous film. The initial highly doped layer provides high conductivity, enabling a good charge transfer path from the bottom. This gradient doping design, with the doping concentration gradually decreasing, optimizes the electrochemically active surface while maintaining overall conductivity. The porous structure, combined with the highly conductive layered structure, facilitates electrolyte wetting, reactant transport, and rapid charge transfer. The structural features shown in the image (high porosity and interconnected network) offer significant advantages in this regard, contributing to the synergistic optimization of a wide potential window and low background current. Example 2

[0042] The preparation method of the BBD electrode is the same as that in Example 1.

[0043] The electrochemical performance test diagram of the prepared BDD electrode is shown in Figure 2 shown.

[0044] Electrolysis Application: Using the method described in Example 1, a self-prepared BDD electrode was used as the anode, and a platinum electrode was used as the cathode to construct a dual-chamber H-type electrolytic cell. A Nafion membrane was used to separate the anode and cathode compartments. The electrolytes for both the cathode and anode compartments were 0.2 M sodium acetate and 0.3 M glacial acetic acid. Electrolysis was performed continuously for 12 hours at a current density of 200 mA / cm², a temperature of 40°C, and an electrolyte flow rate of 4.5 L / min. Results showed that ethane and carbon dioxide were detected as the main gaseous products in the anode compartment, while hydrogen evolved in the cathode compartment. This indicates that the typical Kolbe electrolysis reaction proceeded smoothly, with an overall feedstock conversion of 75% and a selectivity of 72% for the target product, ethane. After 300 hours of continuous operation, no significant structural changes occurred in the BDD anode, demonstrating the excellent stability and corrosion resistance of this system in long-term Kolbe electrolysis applications. Example 3

[0045] The difference from Example 1 is that the electrochemical treatment current density during the pretreatment of the porous titanium substrate is different, specifically as follows: during the electrochemical treatment process, the electrochemical treatment temperature is controlled at 25°C, the electrochemical treatment current density is controlled at 100 A / m², and the electrochemical treatment is carried out for 2 hours.

[0046] Electrolysis applications: A dual-chamber H-type electrolytic cell was constructed using the homemade BDD electrode from Example 3 as the anode and a platinum electrode as the cathode, with a Nafion membrane separating the anode and cathode regions. The electrolytes for both the cathode and anode compartments were 0.2 M sodium acetate and 0.3 M glacial acetic acid. Electrolysis was performed continuously for 12 hours at a current density of 200 mA / cm², a temperature of 40°C, and an electrolyte flow rate of 4.5 L / min. The results showed that ethane and carbon dioxide were detected as the main gaseous products in the anode region, while hydrogen was released in the cathode region, indicating that the typical Kolbe electrolysis reaction proceeded smoothly, with an overall feedstock conversion of 61% and a selectivity of 65% for the target product, ethane. Example 4

[0047] The difference from Example 1 is that the deposition temperature of the pretreated porous titanium is different during the preparation of the TiN thin film layer. Specifically, the pretreated porous titanium substrate is placed in the atomic layer deposition reaction chamber, the chamber door is closed, the vacuum pump is started, and the chamber is evacuated to 10 -3 Pa to ensure that there is no impurity gas in the reaction chamber to interfere with the deposition process. The deposition temperature of the substrate is slowly heated to 250 ° C to avoid cracks in the substrate due to thermal stress.

[0048] Electrolysis applications: A dual-chamber H-type electrolytic cell was constructed using the homemade BDD electrode from Example 4 as the anode and a platinum electrode as the cathode, with a Nafion membrane separating the anode and cathode regions. The electrolytes for both the cathode and anode compartments were prepared as 0.2 M sodium acetate and 0.3 M glacial acetic acid. Electrolysis was performed continuously for 12 hours at a current density of 200 mA / cm², a temperature of 40°C, and an electrolyte flow rate of 4.5 L / min. The results showed that ethane and carbon dioxide were detected as the main gaseous products in the anode region, while hydrogen was released in the cathode region, indicating that the typical Kolbe electrolysis reaction proceeded smoothly, with an overall feedstock conversion of 55% and a selectivity of 60% for the target product, ethane. Example 5

[0049] The difference from Example 1 is that the concentration of the single-walled carbon nanotube dispersion during the deposition of single-walled carbon nanotubes is different, specifically as follows: the porous titanium substrate obtained in step (2) is placed in an electrophoresis tank containing 0.1 mg / mL single-walled carbon nanotube dispersion and 1% sodium dodecyl sulfate, and ultrasonically treated at a power of 200 W for 10 minutes to ensure uniform dispersion of SWCNTs.

[0050] Electrolysis applications: A dual-chamber H-type electrolytic cell was constructed using the homemade BDD electrode from Example 5 as the anode and a platinum electrode as the cathode, with a Nafion membrane separating the anode and cathode regions. The electrolytes for both the cathode and anode compartments were 0.2 M sodium acetate and 0.3 M glacial acetic acid. Electrolysis was performed continuously for 12 hours at a current density of 200 mA / cm², a temperature of 40°C, and an electrolyte flow rate of 4.5 L / min. The results showed that ethane and carbon dioxide were detected as the main gaseous products in the anode region, while hydrogen was released in the cathode region, indicating that the typical Kolbe electrolysis reaction proceeded smoothly. The overall feedstock conversion was 66%, and the selectivity for the target product, ethane, was 68%. Example 6

[0051] The difference from Example 1 is that the deposition temperature during the preparation of the highly doped BDD layer is different, specifically as follows: during the deposition process, the chamber deposition temperature is controlled at 400°C.

[0052] Electrolysis applications: A dual-chamber H-type electrolytic cell was constructed using the homemade BDD electrode from Example 6 as the anode and a platinum electrode as the cathode, with a Nafion membrane separating the anode and cathode regions. The electrolytes for both the cathode and anode compartments were 0.2 M sodium acetate and 0.3 M glacial acetic acid. Electrolysis was performed continuously for 12 hours at a current density of 200 mA / cm², a temperature of 40°C, and an electrolyte flow rate of 4.5 L / min. The results showed that ethane and carbon dioxide were detected as the main gaseous products in the anode region, while hydrogen was released in the cathode region, indicating that the typical Kolbe electrolysis reaction proceeded smoothly, with an overall feedstock conversion of 56% and a selectivity for the target product, ethane, of 59%. Example 7

[0053] The difference from Example 1 is that the number of cycles in the process of preparing the multilayer SWCNT / BDD composite structure is different, specifically as follows: Step (3) and Step (4) are repeated 5 times to form a multilayer SWCNT / BDD composite structure.

[0054] Electrolysis applications: A dual-chamber H-type electrolytic cell was constructed using the homemade BDD electrode from Example 7 as the anode and a platinum electrode as the cathode, with a Nafion membrane separating the anode and cathode regions. The electrolytes for both the cathode and anode chambers were 0.2 M sodium acetate and 0.3 M glacial acetic acid. Electrolysis was performed continuously for 12 hours at a current density of 200 mA / cm², a temperature of 40°C, and an electrolyte flow rate of 4.5 L / min. The results showed that ethane and carbon dioxide were detected as the main gaseous products in the anode region, while hydrogen was released in the cathode region, indicating that the typical Kolbe electrolysis reaction proceeded smoothly, with an overall feedstock conversion of 64% and a selectivity of 67% for the target product, ethane. Example 8

[0055] The difference from Example 1 is that the deposition time during the preparation of the BDD active layer is different, specifically as follows: during the deposition process, the chamber deposition temperature is controlled at 850°C, the deposition gas pressure is maintained at 3 kPa, the deposition time is set to 1 hour, and a low-doped BDD layer is grown.

[0056] Electrolysis applications: A dual-chamber H-type electrolytic cell was constructed using the homemade BDD electrode from Example 8 as the anode and a platinum electrode as the cathode, with a Nafion membrane separating the anode and cathode regions. The electrolytes for both the cathode and anode compartments were 0.2 M sodium acetate and 0.3 M glacial acetic acid. Electrolysis was performed continuously for 12 hours at a current density of 200 mA / cm², a temperature of 40°C, and an electrolyte flow rate of 4.5 L / min. The results showed that ethane and carbon dioxide were detected as the main gaseous products in the anode region, while hydrogen was released in the cathode region, indicating that the typical Kolbe electrolysis reaction proceeded smoothly, with an overall feedstock conversion of 62% and a selectivity of 66% for the target product, ethane. Example 9

[0057] The difference from Example 1 is that no TiN thin film layer is prepared. Specifically, single-walled carbon nanotubes are directly deposited on the porous titanium substrate obtained in step (1).

[0058] Electrolysis applications: A dual-chamber H-type electrolytic cell was constructed using the homemade BDD electrode from Example 9 as the anode and a platinum electrode as the cathode, with a Nafion membrane separating the anode and cathode regions. The electrolytes for both the cathode and anode chambers were 0.2 M sodium acetate and 0.3 M glacial acetic acid. Electrolysis was performed continuously for 12 hours at a current density of 200 mA / cm², a temperature of 40°C, and an electrolyte flow rate of 4.5 L / min. The results showed that ethane and carbon dioxide were detected as the main gaseous products in the anode region, while hydrogen was released in the cathode region, indicating that the typical Kolbe electrolysis reaction proceeded smoothly, with an overall feedstock conversion of 35% and a selectivity of 39% for the target product, ethane.

[0059] The comparative analysis of Example 1 and Examples 3-8 is shown in Table 1.

[0060] Table 1 is a comparative analysis of Example 1 and Examples 3-8 Example Adjustment Point Selectivity (%) Conversion rate (%) Electrode life in conclusion 1 none 70 72 No significant changes after 300 hours Excellent balance performance and optimal comprehensive indicators 3 The electrochemical treatment current density during the pretreatment of the porous titanium substrate is different, from 200A / m² to 100A / m² 61 65 Surface slight deformation after 300h Reducing the current density of the pretreatment will reduce the surface roughness and affect the subsequent deposition. 4 The deposition temperature of the pretreated porous titanium is different, from 260℃ to 250℃ 55 60 Surface cracking after 300h When the deposition temperature is lowered, the uniformity and density of the TiN film deteriorate and the crystallinity decreases. 5 The concentration of the single-walled carbon nanotube dispersion is different, from 1 mg / mL single-walled carbon nanotube dispersion to 0.1 mg / mL single-walled carbon nanotube dispersion 66 68 Surface discoloration after 300h The decrease in SWCNT dispersion concentration resulted in thinner and less uniform coatings, and weakened adhesion. 6 The deposition temperature during the preparation of the highly doped BDD layer was changed from 700°C to 400°C. 56 59 Surface cracking after 300h Lowering the deposition temperature leads to a lower growth rate, requiring more time to reach the same thickness, which reduces the stress in the BDD layer but affects the bonding strength. 7 The number of cycles in the preparation of multilayer SWCNT / BDD composite structures is different, from 10 to 5 64 67 Surface deformation after 300h Reducing the number of cycles will result in thinner composite structures, insufficient mechanical strength and toughness, and poor surface uniformity and coverage. 8 The deposition time during the preparation of the BDD active layer was changed from 2 hours to 1 hour. 62 66 Surface slight deformation after 300h Deposition time affects the thickness of the BDD active layer. Thicker BDD active layers provide better electrical performance. Thinner BDD active layers lead to decreased electrical performance. The BDD layer's electrical conductivity decreases, impacting charge transfer efficiency. 9 No TiN thin film layer is prepared 35 39 Surface deformation after 300h The TiN thin film layer improves the charge transfer efficiency of the electrode. In the absence of the TiN layer, the charge transfer rate of the BDD electrode is reduced, resulting in a decrease in the efficiency of the electrocatalytic reaction. It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0061] It should be noted that the above content merely illustrates the technical idea of ​​the present invention and cannot be used to limit the scope of protection of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a BDD electrode material, characterized in that: The following steps are involved: S01, pretreatment of the surface of the porous titanium substrate, pretreatment of the surface of the porous titanium substrate by electrochemical anodic oxidation activation treatment method; S02. Preparation of TiN thin film: In an atomic layer deposition reaction chamber, a 5-10 nm nanoscale titanium nitride thin film layer is pre-deposited on the surface of the pre-treated porous titanium substrate with the assistance of laser pulses; S03, depositing SWCNT network: depositing a layer of 50-100 nm single-walled carbon nanotube network on the TiN thin film layer using electrophoretic deposition; S04. Preparation of boron-doped diamond layer: Using plasma-enhanced chemical vapor deposition technology, a highly doped BDD layer with a thickness of 1-1.5 μm is grown on the single-walled carbon nanotube network; S05, preparing a multilayer SWCNT / BDD composite structure, repeating steps S03 and S04 to form a multilayer SWCNT / BDD composite structure, wherein the thickness of the multilayer SWCNT / BDD composite structure is controlled to be 1-50 μm; S06. Preparation of BDD active layer: Finally, a hot wire chemical vapor deposition technique is used to deposit a 1-5 μm low-doped BDD active layer on the multilayer SWCNT / BDD composite structure to obtain a BBD electrode.

2. The method for preparing a BDD electrode material according to claim 1, characterized in that: Step S01 also includes the following steps: using the porous titanium substrate as the anode and the inert electrode graphite as the cathode, using a neutral electrolyte; performing electrochemical treatment at a temperature of 20-25°C, applying a constant current density of 100-200 A / m 2 The treatment time is 1-2 hours, an oxide layer is formed on the titanium surface, and after treatment, low-temperature annealing is performed at 350-400°C for 0.5-1h.

3. The method for preparing a BDD electrode material according to claim 1, characterized in that: Step S02 also includes the following steps: placing the pretreated porous titanium substrate in an atomic layer deposition reaction chamber, using TiCl4 as a Ti precursor and NH3 as a N precursor, the deposition temperature is 250-300°C, and under femtosecond laser pulse conditions, NH3 reacts with TiCl4 adsorbed on the surface of the substrate to form a TiN thin film layer. In order to achieve the required film thickness, the above atomic layer deposition cycle is repeated multiple times. Each atomic layer deposition cycle includes: TiCl4 pulse 0.1 s - purification 3 s - NH3 pulse 1 s - laser irradiation 0.5 s - purification 3 s, and the laser energy density is controlled at 50-100 mJ / cm².

4. The method for preparing a BDD electrode material according to claim 3, characterized in that: The femtosecond laser pulse conditions include: wavelength 800 nm, pulse width 100 fs, and repetition frequency 1 kHz.

5. The method for preparing a BDD electrode material according to claim 1, characterized in that: Step S03 also includes the following steps: placing the porous titanium substrate obtained in step S02 in an electrophoresis tank containing 0.1-1 mg / mL single-walled carbon nanotubes and 1%-5% sodium dodecyl sulfate dispersion, and using a power of 200W-400W for ultrasonic treatment for 10-30 minutes; using the ultrasonically treated porous titanium substrate as a cathode and a platinum electrode as an anode, immersing them in a dispersion containing 0.1-1 mg / mL single-walled carbon nanotubes and 1%-5% sodium dodecyl sulfate, maintaining the distance between the anode and the cathode at 1-5 cm, applying a DC voltage of 20-50V, and controlling the deposition time to be 5-15 minutes. After the deposition is completed, the porous titanium substrate is washed with deionized water, and then dried at 60-80°C for 10-20 minutes, and heat-treated at 300-500°C for 1-2 hours to complete the deposition of the SWCNT network to obtain a SWCNT network porous titanium substrate.

6. The method for preparing a BDD electrode material according to claim 1, characterized in that: Step S04 also includes the following steps: drying the SWCNT network porous titanium substrate obtained in step S03 and placing it in an HFCVD chamber, closing the chamber door, starting the vacuum pump to evacuate the chamber, and then introducing a doping boron source, a carbon source, and a carrier gas; turning on the RF power supply to perform deposition; during the deposition process, the deposition temperature is controlled at 400-700°C, the deposition pressure is maintained at 1-5KPa, the deposition time is set to 1-5 hours, and the deposition rate is expected to be 10-30 nm / min, growing a highly doped BDD layer, and after the deposition is completed, ultrasonically cleaning with deionized water for 5 minutes at an ultrasonic frequency of 40kHz. After cleaning, the porous titanium substrate is blown dry with nitrogen.

7. The method for preparing a BDD electrode material according to claim 6, characterized in that: The doping boron source is an ethanol solution of boron trioxide, the carbon source is methane, the carrier gas is hydrogen, and the gas flow ratio of boron trioxide, methane, and hydrogen is 4000-5000:1:

10.

8. The method for preparing a BDD electrode material according to claim 1, characterized in that: Step S06 also includes the following steps: drying the multilayer SWCNT / BDD composite structure substrate obtained in step S05 and placing it in an HFCVD chamber, closing the chamber door, starting the vacuum pump to evacuate the chamber, introducing the reaction gas, turning on the RF power supply, and performing deposition. During the deposition process, the chamber deposition temperature is controlled at 800-850°C, the deposition pressure is maintained at 1-5KPa, and the deposition time is set to 1-5 hours to grow a low-doped BDD layer. The deposition rate is expected to be 5-20 nm / min. After the deposition is completed, ultrasonic cleaning is performed with deionized water for 10 minutes at an ultrasonic frequency of 25kHz. After the cleaning is completed, the BBD electrode is blown dry with nitrogen.

9. The method for preparing a BDD electrode material according to claim 8, characterized in that: The reaction gases are methane and B2H6, and the gas flow ratio of methane to B2H6 is 1:1000-1:2000.

10. A BDD electrode material prepared by the preparation method according to any one of claims 1 to 9.

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