A method for preparing a porous silicon carbide substrate boron-doped diamond thin film electrode

Abstract

The application provides a preparation method of a porous silicon carbide substrate boron-doped diamond thin film electrode, and relates to the technical field of diamond thin film electrodes. The method comprises the following steps: obtaining silica powder, carbon powder and aluminum powder, and mixing the powders to obtain mixed powder; adding the mixed powder into diluted hydroxymethyl cellulose to obtain mixed colloid; according to a preset three-dimensional model, performing three-dimensional printing on the mixed colloid to obtain a precursor, and drying the precursor to obtain a precursor blank; sintering the precursor blank in an inert gas atmosphere to obtain a porous silicon carbide substrate; performing cleaning treatment on the porous silicon carbide substrate, and depositing a boron-doped diamond thin film on the substrate to obtain a boron-doped diamond thin film electrode. The porous silicon carbide substrate is prepared through a simple sintering process, the technical limitations of the existing boron-doped diamond thin film electrode, such as limited specific surface area and low space utilization rate, are broken, and the three-dimensional printing technology is combined to realize mold-free forming of a complex structure.

Description

Technical Field

[0001] This application relates to the field of diamond thin film electrode technology, and more specifically, to a method for preparing a boron-doped diamond thin film electrode on a porous silicon carbide substrate. Background Technology

[0002] Boron-doped diamond (BDD) thin-film electrodes have shown broad application prospects in the field of electrochemistry due to their outstanding advantages such as wide electrochemical potential window, high oxygen evolution overpotential, low background current, excellent mechanical strength, chemical inertness and long-term stability. They have been initially applied in many scenarios such as wastewater treatment, CO2 reduction, electrochemical sensing, electrochemical energy storage and synthesis.

[0003] Currently, commercially available or research-based BDD electrodes mostly employ traditional two-dimensional planar structures on their SiC substrates. This flat structure results in a limited specific surface area and low space utilization, severely restricting the number of generation sites for active species such as hydroxyl radicals (·OH) during electrolysis. It also reduces the effective contact area between the reactants and the electrode surface, thus hindering further improvements in the oxidation efficiency of BDD electrodes.

[0004] Therefore, existing BDD electrode fabrication technologies still have significant shortcomings in balancing high specific surface area, excellent interfacial bonding strength, long-term stability, low cost, and mass production feasibility. There is an urgent need to develop a novel BDD electrode and its fabrication method that can overcome the limitations of two-dimensional structures, realize three-dimensional reaction channels, and is simple to process and suitable for large-scale production.

[0005] There is currently no effective technical solution to the above problems. Summary of the Invention

[0006] The purpose of this application is to provide a method for preparing boron-doped diamond thin film electrodes on porous silicon carbide substrates, aiming to solve the technical problems of existing boron-doped diamond thin film electrodes, such as limited specific surface area, low space utilization, limited oxidation efficiency, complex preparation process, high cost, and difficulty in mass production.

[0007] In a first aspect, this application provides a method for preparing a boron-doped diamond thin film electrode on a porous silicon carbide substrate, comprising the following steps:

[0008] S1. Obtain silicon dioxide powder, carbon powder and aluminum powder, and mix the silicon dioxide powder, carbon powder and aluminum powder to obtain mixed powder;

[0009] S2. Obtain hydroxymethylcellulose and deionized water in a preset ratio, dilute the hydroxymethylcellulose with deionized water, add the mixed powder to the diluted hydroxymethylcellulose to obtain a mixed colloid;

[0010] S3. Based on the preset three-dimensional model, use the mixed colloid for three-dimensional printing to obtain the precursor, and dry the precursor to obtain the precursor blank.

[0011] S4. The precursor blank is sintered in an inert gas atmosphere to obtain a porous silicon carbide substrate.

[0012] S5. The porous silicon carbide substrate is cleaned and a boron-doped diamond film is deposited on the porous silicon carbide substrate to obtain a boron-doped diamond film electrode.

[0013] This technical solution achieves a three-dimensional reaction channel, significantly improving the specific surface area and space utilization of the electrode. This increases the number of active species generation sites and the effective contact area between the reactants and the electrode surface, laying the foundation for improving the oxidation efficiency of boron-doped diamond thin film electrodes. Furthermore, the method is simple and has good potential for mass production.

[0014] Optionally, step S1 includes:

[0015] Silica powder with a particle size of no more than 20 nm was selected as the silicon source, fibrous carbon powder with a particle size of no more than 200 mesh, and aluminum powder with a particle size of no more than 25 μm. The silica powder, carbon powder and aluminum powder were mixed in a mass ratio of 2.5:1:1 and then ball-milled for 6-8 hours to obtain the mixed powder.

[0016] This technical solution facilitates the formation of porous silicon carbide substrates with uniform structure and excellent performance, thereby improving the overall performance of the final boron-doped diamond thin film electrode.

[0017] Optionally, step S2 includes:

[0018] Obtain hydroxymethyl cellulose of the same mass as the toner, dissolve it in deionized water at a 1:1 ratio, stir well to obtain a mixed liquid;

[0019] Pour the mixed powder into the mixed liquid and stir continuously during the pouring process to obtain a uniform mixed colloid.

[0020] This technical solution optimizes the preparation process of the mixed colloid, providing a colloid with good flowability and high printing accuracy for 3D printing. It effectively avoids clogging or delamination that may occur during the printing process, ensuring the molding quality of the precursor.

[0021] Optionally, step S3 includes:

[0022] Based on the preset 3D model, determine the printing path information of the 3D model;

[0023] Based on the printing path information, the printing parameters are adjusted, and the mixed colloid is deposited and shaped using 3D printing technology to obtain the precursor.

[0024] The precursor was left to stand at room temperature.

[0025] The precursor, after being left to stand, is dried to obtain a precursor blank.

[0026] By determining the printing path information and adjusting the jetting speed, precise control over the shape and structure of the precursor was achieved. Simultaneously, the introduction of room temperature settling treatment contributes to the stability of the precursor structure, providing a more stable foundation for subsequent drying and sintering, and reducing the risk of cracking and deformation.

[0027] Optionally, the step of drying the precursor after static treatment to obtain the precursor blank includes:

[0028] The precursor, after being left to stand, is dried at a temperature between 80℃ and 90℃ and for a drying time between 5h and 10h to obtain a precursor blank.

[0029] Optionally, the printing parameters include the jetting speed of the mixed colloid, the printing speed, and the layer height, wherein the jetting speed of the mixed colloid is 7mm / s-12mm / s.

[0030] Optionally, step S4 includes:

[0031] The precursor preform is placed in a tube furnace and evacuated to a preset range.

[0032] Argon gas is introduced, and segmented sintering is carried out under argon atmosphere to obtain a porous silicon carbide substrate.

[0033] Optionally, the segmented sintering step includes:

[0034] The temperature was raised from room temperature to 1000℃ at the first preset heating rate and held for 1 hour.

[0035] Then, raise the temperature from 1000℃ to 1400℃ at the first preset heating rate and hold for 1 hour;

[0036] Then, the temperature is increased from 1400℃ to 1500℃ at the second preset heating rate, kept at that temperature for 3-4 hours, and then cooled to room temperature.

[0037] Optionally, step S5 includes:

[0038] Use anhydrous ethanol to clean the porous silicon carbide substrate in an ultrasonic bath for 5-10 minutes to remove residual substances from the surface.

[0039] The cleaned porous silicon carbide substrate is placed in the cavity of a microwave plasma chemical vapor deposition system. The microwave plasma chemical vapor deposition system deposits a boron-doped diamond film on the porous silicon carbide substrate according to preset parameters to obtain a boron-doped diamond film electrode.

[0040] Optionally, the preset parameters include:

[0041] To achieve a vacuum level of 1*10 in the cavity of the microwave plasma chemical vapor deposition system. -3 -4*10 -3 Pa;

[0042] Methane with a flow rate of 6 sccm and hydrogen with a flow rate of 200 sccm were selected as the reaction gases, and diborane was used as the boron source. The flow rate of diborane was 2 sccm-4 sccm, the deposition power was 8 kW-10 kW, the chamber pressure was 70 Torr-80 Torr, and the deposition time was 3 h-5 h.

[0043] As described above, the method for preparing a porous silicon carbide substrate boron-doped diamond thin film electrode provided in this application involves: obtaining and mixing silica powder, carbon powder, and aluminum powder to obtain a mixed powder; then, adding the mixed powder to diluted hydroxymethyl cellulose to obtain a mixed colloid; next, using the mixed colloid for 3D printing according to a preset 3D model to obtain a precursor, and drying it to obtain a precursor blank; then, sintering the precursor blank in an inert gas atmosphere to obtain a porous silicon carbide substrate; finally, cleaning the porous silicon carbide substrate and depositing a boron-doped diamond thin film on it to obtain a boron-doped diamond thin film electrode. A three-dimensional porous SiC substrate structure is obtained through a simple sintering process, forming a "three-dimensional reaction channel," breaking through the limitations of electrochemical reaction efficiency of traditional two-dimensional SiC structure BDD electrodes and achieving an exponential increase in area. Furthermore, combined with 3D printing technology, it enables moldless molding of complex structures, solving the problem of traditional porous SiC substrates being limited by mold forming, and allowing for flexible customization of 3D SiC / BDD electrode structures according to actual needs.

[0044] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing embodiments of this application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0045] Figure 1 This is a flowchart illustrating a method for preparing a porous silicon carbide substrate boron-doped diamond thin film electrode according to an embodiment of this application.

[0046] Figure 2This is a schematic diagram of the morphology of the porous silicon carbide substrate before deposition, provided in an embodiment of this application.

[0047] Figure 3 This is a schematic diagram of the morphology of the porous silicon carbide substrate after deposition, provided in an embodiment of this application.

[0048] Figure 4 A table comparing the elemental content of porous silicon carbide substrates before and after deposition, provided for embodiments of this application.

[0049] Figure 5 The double-layered sheet-like precursor preform provided in the embodiments of this application. Detailed Implementation

[0050] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0051] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0052] Firstly, referring to Figure 1 This application provides a method for preparing a boron-doped diamond thin film electrode on a porous silicon carbide substrate, comprising the following steps:

[0053] S1. Obtain silicon dioxide powder, carbon powder and aluminum powder, and mix the silicon dioxide powder, carbon powder and aluminum powder to obtain mixed powder;

[0054] S2. Obtain hydroxymethylcellulose and deionized water in a preset ratio, dilute the hydroxymethylcellulose with deionized water, add the mixed powder to the diluted hydroxymethylcellulose to obtain a mixed colloid;

[0055] S3. Based on the preset three-dimensional model, use the mixed colloid for three-dimensional printing to obtain the precursor, and dry the precursor to obtain the precursor blank.

[0056] S4. The precursor blank is sintered in an inert gas atmosphere to obtain a porous silicon carbide substrate.

[0057] S5. The porous silicon carbide substrate is cleaned and a boron-doped diamond film is deposited on the porous silicon carbide substrate to obtain a boron-doped diamond film electrode.

[0058] This application prepares a three-dimensional porous SiC substrate through a precursor sintering process, which greatly increases the actual specific surface area of ​​the substrate, thereby effectively increasing the number of active sites and the contact area of ​​reactants. Furthermore, by combining it with three-dimensional printing technology, it breaks through the limitations of structural design to achieve moldless molding of complex structures, providing a new way to improve the oxidation efficiency of boron-doped diamond thin film electrodes. The porous precursor formed by the sintering of mixed colloids greatly increases the actual specific surface area of ​​the substrate.

[0059] "Porous silicon carbide substrate" refers to a substrate material with a porous structure and silicon carbide as its main component. Its porous nature helps to increase the specific surface area of ​​the electrodes, providing support for the subsequent deposition of diamond films. "3D printing" is an additive manufacturing technology that can build three-dimensional objects layer by layer according to a digital model. In this application, it is used to construct a complex three-dimensional structure of a porous silicon carbide substrate.

[0060] Specifically, in step S1, it is necessary to obtain silica powder, carbon powder, and aluminum powder, and then mix them to obtain a mixed powder. There are various ways to obtain the silica powder, carbon powder, and aluminum powder. For example, commercially available silica powder, carbon powder, and aluminum powder that meet the required purity can be purchased directly. During the mixing process, mechanical stirring, ball milling, or other methods can be used to ensure that the three powders are uniformly mixed. For example, the three powders can be manually ground in a mortar or ball milled using a planetary ball mill to achieve thorough mixing.

[0061] In step S2, a predetermined ratio of hydroxymethylcellulose (HMC) and deionized water is obtained. The HMC is diluted with deionized water, and the mixed powder is added to the diluted HMC to obtain a mixed colloid. The ratio of HMC to deionized water, acting as a binder, can be adjusted according to the desired colloid viscosity. For example, HMC can be dissolved in deionized water at a mass ratio of 1:10 and stirred thoroughly until completely dissolved. Subsequently, the mixed powder obtained in step S1 is slowly added to the diluted HMC solution while stirring to ensure the powder is uniformly dispersed in the solution, forming a stable mixed colloid.

[0062] In step S3, based on a preset 3D model, a mixed colloid is used for 3D printing to obtain a precursor. The precursor is then dried to obtain a precursor blank. The preset 3D model can be created using computer-aided design (CAD) software, which defines the geometry and internal structure of the final porous silicon carbide substrate. During 3D printing, an extrusion-type 3D printer can be used to extrude the mixed colloid through a nozzle, stacking it layer by layer according to the path of the 3D model. For example, the printer's ejection speed can be set to 5 mm / s, and the layer thickness to 0.2 mm, printing the required precursor layer by layer. After printing, the precursor usually contains a large amount of moisture and needs to be dried. Drying can be done by air drying at room temperature or by low-temperature drying in an oven. For example, the precursor can be placed in a well-ventilated environment and left to stand for 24 hours to allow it to dry initially, and then placed in an 80°C oven for 6 hours to completely remove moisture and obtain a precursor blank with a certain strength.

[0063] In step S4, the precursor preform is sintered in an inert gas atmosphere to obtain a porous silicon carbide substrate. Sintering is a crucial step in densifying the precursor preform and causing a phase transformation to form silicon carbide. An inert gas atmosphere, such as argon or nitrogen, prevents the precursor from oxidizing at high temperatures. The sintering process can be carried out in a tube furnace or a box furnace. For example, the precursor preform is placed in a graphite crucible, and then the crucible is placed in a tube furnace. After evacuation, argon gas is introduced, and the furnace temperature is slowly raised from room temperature to 1500°C and held at this temperature for 3 hours. Then, it is allowed to cool naturally to room temperature to obtain the porous silicon carbide substrate.

[0064] In step S5, the porous silicon carbide substrate is cleaned, and a boron-doped diamond film is deposited on the porous silicon carbide substrate to obtain a boron-doped diamond film electrode. The purpose of the cleaning process is to remove impurities that may remain on the substrate surface during sintering. For example, the porous silicon carbide substrate can be ultrasonically cleaned for 10 minutes using deionized water or ethanol, and then dried with nitrogen. The deposition of the boron-doped diamond film is usually performed using microwave plasma chemical vapor deposition (MPCVD). For example, the cleaned porous silicon carbide substrate is placed in the cavity of an MPCVD system, and a mixed gas of methane, hydrogen, and diborane (as a boron source) is introduced. Deposition is carried out at a preset microwave power, cavity pressure, and temperature. For example, the methane flow rate can be set to 5 sccm, the hydrogen flow rate to 200 sccm, the diborane flow rate to 3 sccm, the deposition power to 9 kW, the cavity pressure to 75 Torr, and the deposition time to 4 hours, thereby forming a uniform boron-doped diamond film on the surface of the porous silicon carbide substrate, ultimately obtaining a boron-doped diamond film electrode.

[0065] The method for fabricating boron-doped diamond thin-film electrodes on porous silicon carbide substrates in this application effectively solves the problems of limited specific surface area and low space utilization of boron-doped diamond thin-film electrodes in the prior art through a series of synergistic steps. First, steps S1 and S2 prepare a stable mixed colloid by precisely proportioning and thoroughly mixing silica powder, carbon powder, aluminum powder, hydroxymethyl cellulose, and deionized water. This colloid not only provides suitable rheological properties for subsequent 3D printing but also lays the material foundation for the final formation of the porous silicon carbide substrate.

[0066] Subsequently, in step S3, using 3D printing technology, the mixed colloid is precisely deposited layer by layer to form a precursor according to a preset 3D model. Through 3D printing, substrate shape frameworks with complex geometries and multi-channel features can be designed and manufactured. The precursor blank obtained after drying has a certain mechanical strength, providing structural support for subsequent high-temperature sintering.

[0067] Next, in step S4, the precursor preform is sintered in an inert gas atmosphere, promoting a carbothermic reduction reaction to form a porous silicon carbide substrate with high porosity and a stable structure. The inert gas atmosphere effectively avoids high-temperature oxidation, ensuring the purity and structural integrity of the silicon carbide. The formation of the porous silicon carbide substrate greatly increases the specific surface area of ​​the electrode, providing abundant adhesion sites for subsequent diamond film deposition.

[0068] Finally, in step S5, the porous silicon carbide substrate is cleaned to remove surface impurities, ensuring good adhesion of the diamond film. Subsequently, a boron-doped diamond film is deposited on the porous silicon carbide substrate using chemical vapor deposition. Because the substrate itself has a three-dimensional porous structure, the deposited diamond film also forms a three-dimensional structure, resulting in a final boron-doped diamond film electrode with high specific surface area and three-dimensional reaction channels.

[0069] Overall, a simple sintering process yields a three-dimensional porous SiC substrate structure forming a "three-dimensional reaction channel," overcoming the limitations of electrochemical reaction efficiency in traditional two-dimensional SiC BDD electrodes and achieving an exponential increase in area. Furthermore, combined with 3D printing technology, it enables moldless fabrication of complex structures, overcoming the limitations of traditional porous SiC substrates that rely on molds. This allows for flexible customization of 3D SiC / BDD electrode structures according to actual needs, significantly improving the electrode's specific surface area and space utilization. This structure not only increases the number of generation sites for active species such as hydroxyl radicals during electrolysis but also expands the effective contact area between reactants and the electrode surface, thereby effectively improving the oxidation efficiency of boron-doped diamond thin film electrodes. The fabrication method described in this application is easy to operate, requiring no complex etching or template removal processes. Moreover, 3D printing technology allows for consistent control of shape, size, and pore structure across batches of porous silicon carbide substrates, facilitating large-scale mass production.

[0070] In some implementations, step S1 includes:

[0071] Silica powder with a particle size of no more than 20 nm was selected as the silicon source, fibrous carbon powder with a particle size of no more than 200 mesh, and aluminum powder with a particle size of no more than 25 μm. The silica powder, carbon powder and aluminum powder were mixed in a mass ratio of 2.5:1:1 and then ball-milled for 6-8 hours to obtain the mixed powder.

[0072] Specifically, silica powder was selected as the silicon source, with a particle size limited to no more than 20 nm. This small particle size of silica powder provides a larger specific surface area, which is beneficial for its full reaction with carbon and aluminum powder during subsequent sintering to form silicon carbide. The carbon powder was selected to be fibrous, with a mesh size no greater than 200 mesh. Fibrous carbon powder has good dispersibility and contact area with silica powder, while the smaller mesh size (i.e., larger particle size) helps to form a porous structure during sintering. The aluminum powder's particle size was limited to no more than 25 μm; as a reducing agent and sintering aid, its small particle size helps it to be uniformly dispersed and participate in the reaction.

[0073] The mass ratio of silicon dioxide powder, carbon powder, and aluminum powder was set to 2.5:1:1. This ratio was optimized to ensure that the silicon, carbon, and aluminum sources could fully react during the high-temperature sintering process to form a high-purity, high-porosity silicon carbide substrate.

[0074] This application's solution effectively solves the problem of insufficient powder uniformity in traditional methods by precisely controlling the particle size, morphology, mixing ratio, and mixing method of silica powder, carbon powder, and aluminum powder. Specifically, selecting small-particle-size silica powder and aluminum powder, as well as fibrous carbon powder, significantly increases the contact area between the components, promoting the subsequent sintering reaction. Precisely controlling the mass ratio to 2.5:1:1 ensures optimized reactant proportions, which is beneficial for forming a stable silicon carbide structure. Furthermore, introducing a 6-8 hour ball milling process further refines the powder particles and achieves highly uniform mixing at the microscopic level, thereby avoiding sintering defects caused by localized component inhomogeneity and ensuring the structural uniformity and controllable porosity of the porous silicon carbide substrate.

[0075] In some implementations, step S2 includes:

[0076] Obtain hydroxymethyl cellulose of the same mass as the toner, dissolve it in deionized water at a 1:1 ratio, stir well to obtain a mixed liquid;

[0077] Pour the mixed powder into the mixed liquid and stir continuously during the pouring process to obtain a uniform mixed colloid.

[0078] Specifically, obtaining the same mass of hydroxymethyl cellulose (HMC) as the toner is crucial to ensure that the amount of HMC used as a binder matches the amount of toner. This ensures a stable silicon carbide framework is formed during subsequent sintering, avoiding insufficient structural strength due to too little binder or excessive residue after sintering due to too much binder. The 1:1 ratio of HMC to deionized water ensures complete dissolution of the HMC, forming a moderately viscous and homogeneous liquid, providing a good medium for the uniform dispersion of the powder mixture. Continuous stirring during dissolution accelerates the dissolution of HMC and ensures the homogeneity of the liquid mixture. In practical applications, continuous stirring is used when pouring the powder mixture into the liquid mixture to effectively prevent localized agglomeration of the powder upon addition, ensuring uniform dispersion of powder particles and forming a highly homogeneous colloid. This is crucial for the smoothness of subsequent 3D printing and the quality of the printed parts.

[0079] In some preferred embodiments, the specific implementation is as follows: First, 3g of hydroxymethylcellulose is weighed and dissolved in 3ml of deionized water, with continuous stirring until the hydroxymethylcellulose is completely dissolved, thus obtaining a homogeneous liquid mixture. Then, the pre-prepared mixed powder is slowly poured into the liquid mixture in three portions, with continuous stirring during each pour, until no agglomeration or particles are observed in the mixture, ultimately obtaining a highly homogeneous colloid. This operation ensures the uniform distribution of components within the colloid, providing an ideal printing material for subsequent 3D printing steps.

[0080] In some implementations, step S3 includes:

[0081] Based on the preset 3D model, determine the printing path information of the 3D model;

[0082] Based on the printing path information, the printing parameters are adjusted, and the mixed colloid is deposited and shaped using 3D printing technology to obtain the precursor.

[0083] The precursor was left to stand at room temperature.

[0084] The precursor, after being left to stand, is dried to obtain a precursor blank.

[0085] The preset 3D model refers to a pre-designed digital 3D model with a specific pattern and shape. Determining the printing path information of the 3D model means converting the shape data (geometric information) of the 3D model into precise control instructions for the movement trajectory of the print head that the printing equipment can recognize and execute.

[0086] Specifically, determining the printing path information of the 3D model based on the preset 3D model refers to analyzing the preset 3D model using software before 3D printing to generate a layer-by-layer or line-by-line printing path. This guides the printing equipment to accurately deposit the mixed colloid, i.e., to print the target pattern that matches the preset shape. The purpose is to ensure that the printed precursor accurately reproduces the preset 3D structure, avoiding structural deviations caused by improper path planning. This involves adjusting printing parameters based on the printing path information, dynamically adjusting various printing parameters (such as the spraying speed of the mixed colloid, printing speed, layer height, nozzle diameter, etc.), and using 3D printing technology to deposit the mixed colloid into shape. This accurately obtains various specific morphologies (including two-dimensional planar structures or three-dimensional solid structures) of the target precursor. The core purpose of this 3D printing process is to achieve refined control of the electrode morphology. For example, when printing fine structures or corners, the spraying speed can be appropriately reduced to improve accuracy; when filling large areas, the spraying speed can be appropriately increased to improve efficiency. The aim is to optimize the uniformity and density of material deposition, preventing problems such as discontinuity, uneven accumulation, or stringing, thereby ensuring the quality of the precursor molding. In practical applications, the static treatment of the precursor at room temperature refers to placing the obtained precursor in a room-temperature environment after 3D printing without any external intervention, allowing it to stand naturally for a period of time. This allows the solvent in the mixed colloid to slowly evaporate, thereby enhancing the initial strength and resistance to deformation of the precursor and providing a stable foundation for subsequent drying. Further, drying the precursor after static treatment to obtain a precursor preform involves placing the pre-stabilized precursor in a drying device after the static treatment, controlling the temperature and time to remove residual solvent, allowing it to completely solidify and form a precursor preform with sufficient mechanical strength.

[0087] In some embodiments, the step of drying the precursor after static treatment to obtain a precursor blank includes:

[0088] The precursor, after being left to stand, is dried at a temperature between 80℃ and 90℃ and for a drying time between 5h and 10h to obtain a precursor blank.

[0089] Specifically, a drying temperature of 80℃-90℃ refers to controlling the internal temperature of the drying equipment between 80℃ and 90℃ when drying the precursor after static treatment. This temperature range ensures effective evaporation of deionized water inside the precursor while preventing premature decomposition of organic binders (such as hydroxymethyl cellulose) or irreversible damage to the precursor structure due to excessively high temperatures. A drying time of 5h-10h means the drying process should last between 5 and 10 hours. This time range ensures that moisture inside the precursor is fully and evenly removed, thoroughly eliminating moisture and preventing incomplete drying from affecting subsequent sintering processes. By precisely controlling the drying temperature and time, problems such as cracking, deformation, or internal stress accumulation in the precursor during drying can be effectively avoided, providing a high-quality precursor blank for subsequent sintering steps.

[0090] In some implementations, the printing parameters include at least the jetting speed of the mixed colloid, the printing speed, and the layer height, wherein the jetting speed of the mixed colloid is 7 mm / s-12 mm / s.

[0091] Specifically, the jetting velocity of the mixed colloid refers to the linear velocity at which the mixed colloid is ejected from the nozzle and deposited onto the printing platform or the previous layer during the 3D printing process. Limiting this jetting velocity to the range of 7mm / s-12mm / s aims to ensure that the mixed colloid can be deposited in a controlled and stable manner, thereby forming a precursor with a uniform, dense structure and good interlayer bonding.

[0092] In some implementations, step S4 includes:

[0093] The precursor preform is placed in a tube furnace and evacuated to a preset range.

[0094] Argon gas is introduced, and segmented sintering is carried out under argon atmosphere to obtain a porous silicon carbide substrate.

[0095] The preset range is 1×10. -2 Below Pa.

[0096] The proposed method involves placing the precursor preform in a tube furnace and first evacuating it to a predetermined vacuum level. This maximizes the removal of reactive gases such as oxygen and water vapor from the sintering environment, effectively preventing oxidation of the precursor preform during high-temperature sintering and ensuring the purity of the silicon carbide product. Subsequently, high-purity argon gas is introduced to establish a stable inert protective atmosphere within the tube furnace, further preventing the introduction of external impurities and secondary contamination of the precursor preform. It is precisely this strictly controlled, pure, and inert environment that allows subsequent reactions to proceed efficiently and thoroughly. Furthermore, the segmented sintering method allows for precise control of temperature changes during the sintering process. For example, in the lower temperature range (from room temperature to 1000℃), trace amounts of moisture and hydroxymethyl cellulose (as an organic binder) that may remain in the precursor preform will further decompose and volatilize. This process is crucial for removing organic impurities, effectively purifying the reaction environment and preventing defects or product purity issues caused by the decomposition of these organic substances in subsequent high-temperature reactions. Secondly, aluminum powder, acting as a reducing agent, begins a preliminary redox reaction with silicon dioxide (SiO2), marking the start of the silicon-carbon reaction chain and laying the chemical foundation for the subsequent formation of silicon carbide at higher temperatures. In the medium-high temperature range (from 1000℃ to 1400℃), the reduction redox reaction of aluminum powder with silicon dioxide continues, and the reaction intensifies. This means that more silicon dioxide is reduced, providing the necessary silicon source for the formation of silicon carbide. Simultaneously, at this temperature, the system begins to form the cores of silicon carbide (SiC) grains, known as "seed crystals." These seed crystals are the starting points for subsequent silicon carbide crystal growth, and their formation marks the initial precipitation of the silicon carbide phase. In the highest temperature range (from 1400℃ to 1500℃), the silicon carbide formation reaction proceeds completely. This means that residual silicon oxides (such as SiO) and carbon (possibly from carbonization products of the binder) continue to react fully, ensuring maximum conversion of the precursor into silicon carbide. Meanwhile, the already formed SiC seed crystals grow based on this, through continuous surface reactions. These grown SiC grains interconnect, eventually forming a continuous SiC framework structure.

[0097] In some implementations, the segmented sintering step includes:

[0098] The temperature was raised from room temperature to 1000℃ at the first preset heating rate and held for 1 hour.

[0099] Then, raise the temperature from 1000℃ to 1400℃ at the first preset heating rate and hold for 1 hour;

[0100] Then, the temperature is increased from 1400℃ to 1500℃ at the second preset heating rate, kept at that temperature for 3-4 hours, and then cooled to room temperature.

[0101] Specifically, the aforementioned segmented sintering scheme aims to optimize the formation process of porous silicon carbide substrates by precisely controlling the temperature profile. The "first preset heating rate" refers to the heating rate used in the initial and middle stages of sintering. This rate helps to gradually decompose and expel organic matter inside the precursor blank, while avoiding structural cracking or thermal stress concentration caused by rapid heating. For example, this rate can be set to 10℃ / min to ensure the stability of the material during the heating process. "Heating from room temperature to 1000℃ and holding for 1 hour" is the first sintering stage, which aims to promote the initial reaction of the carbon and silicon sources in the precursor and ensure the full decomposition and volatilization of the organic binder, creating favorable conditions for subsequent silicon carbide formation. Holding at this temperature for 1 hour ensures uniform internal temperature of the material. "Heating from 1000℃ to 1400℃ and holding for 1 hour" is the second sintering stage. The temperature range in this stage is conducive to the formation and growth of silicon carbide nuclei, further promoting the carbothermic reduction reaction. Holding at this temperature for 1 hour ensures sufficient time for the redox reaction and crystal growth. The "second preset heating rate" refers to the heating rate used in the later stages of sintering, from 1400℃ to 1500℃. This rate is typically lower than the first preset heating rate, for example, it can be set to 5℃ / min. Its purpose is to allow for a more complete reaction and more precise control over the grain growth and pore structure formation of silicon carbide. "Heating from 1400℃ to 1500℃ and holding for 3-4 hours" is the third sintering stage, and also the crucial high-temperature sintering stage. This temperature range is ideal for the full formation and densification of silicon carbide. The longer holding time (3-4 hours) ensures the complete completion of the carbothermic reduction reaction, enabling the silicon and carbon sources to be efficiently converted into high-purity porous silicon carbide and form a stable porous network structure. "Reducing to room temperature" refers to the furnace body being naturally or controlled to room temperature after sintering. Its purpose is to avoid thermal shock caused by rapid cooling, thereby protecting the structural integrity of the porous silicon carbide substrate.

[0102] By employing the segmented sintering technique described above, and by adding aluminum powder, the maximum sintering temperature is reduced to 1500℃. This lowers the high-temperature resistance requirements of the equipment, reduces production energy consumption, and enables precise control over the microstructure and porosity of the porous silicon carbide substrate. Compared to methods without clearly defined sintering parameters, this approach effectively promotes the full conversion of silicon carbide and the uniform growth of grains, resulting in porous silicon carbide substrates with higher purity, more stable pore structure, and superior mechanical properties. Consequently, the prepared boron-doped diamond thin-film electrode will possess a larger specific surface area and superior electrochemical performance, significantly enhancing its application performance.

[0103] In some implementations, step S5 includes:

[0104] Use anhydrous ethanol to clean the porous silicon carbide substrate in an ultrasonic bath for 5-10 minutes to remove residual substances from the surface.

[0105] The cleaned porous silicon carbide substrate is placed in the cavity of a microwave plasma chemical vapor deposition system. The microwave plasma chemical vapor deposition system deposits a boron-doped diamond film on the porous silicon carbide substrate according to preset parameters to obtain a boron-doped diamond film electrode.

[0106] Depositing boron-doped diamond films involves placing a cleaned porous silicon carbide substrate within the cavity of a microwave plasma chemical vapor deposition (MPCVD) system. MPCVD is an advanced thin-film deposition technology that uses microwave energy to excite reactive gases to form plasma, thereby growing high-quality diamond films on the substrate surface. The deposition of boron-doped diamond films is performed according to preset parameters, including but not limited to cavity vacuum, reactive gas flow rate (such as methane or hydrogen), boron source flow rate (such as diborane), deposition power, cavity pressure, and deposition time. Precise control of these parameters ensures the uniformity, crystallinity, and boron doping concentration of the boron-doped diamond film, resulting in boron-doped diamond film electrodes with excellent electrochemical performance.

[0107] The proposed solution utilizes anhydrous ethanol for ultrasonic cleaning, which penetrates deep into the microscopic pore structure of porous silicon carbide substrates, effectively removing residual substances that are difficult to reach with traditional cleaning methods. This provides a clean surface for subsequent thin film deposition. The improved substrate surface cleanliness allows the boron-doped diamond film to adhere better to the substrate and achieve uniform growth. Furthermore, by employing a microwave plasma chemical vapor deposition system and strictly adhering to preset parameters, reaction conditions can be precisely controlled, ensuring the formation of a dense, uniform diamond film with a specific boron doping concentration on the complex surface of the porous substrate. This controlled deposition process effectively avoids uneven film growth, thus guaranteeing the excellent performance of the final electrode.

[0108] In some implementations, the preset parameters include:

[0109] To achieve a vacuum level of 1*10 in the cavity of the microwave plasma chemical vapor deposition system. -3 -4*10 -3 Pa;

[0110] Methane with a flow rate of 6 sccm and hydrogen with a flow rate of 200 sccm were selected as the reaction gases, and diborane was used as the boron source. The flow rate of diborane was 2 sccm-4 sccm, the deposition power was 8 kW-10 kW, the chamber pressure was 70 Torr-80 Torr, and the deposition time was 3 h-5 h.

[0111] Specifically, the vacuum level of the cavity in the microwave plasma chemical vapor deposition system is set to reach 1*10. -3 -4*10 -3 The purpose of this method is to ensure a highly pure deposition environment, effectively reducing the interference of impurities on the film growth process, thereby promoting the uniform growth and high-quality formation of boron-doped diamond films. Methane and hydrogen are selected as the reactant gases, with a methane flow rate of 6 sccm and a hydrogen flow rate of 200 sccm. Methane serves as the carbon source, providing the necessary carbon atoms for diamond growth; hydrogen plays a crucial role in the plasma, selectively etching non-diamond carbon phases and promoting diamond crystal growth, thus ensuring the purity and crystal quality of the film. Diborane is used as the boron source, with its flow rate controlled between 2 sccm and 4 sccm. This is to precisely control the boron doping concentration in the diamond film to impart the required conductivity. The deposition power is set to 8 kW-10 kW, and the chamber pressure is controlled between 70 Torr-80 Torr. These parameters work together to maintain a stable plasma state, ensuring that the reactant gases are fully activated and efficiently decomposed, thereby achieving uniform deposition of diamond crystals. The deposition time was set to 3-5 hours to ensure that the boron-doped diamond film reached a sufficient thickness to provide stable electrochemical activity and mechanical strength.

[0112] Through the above technical solution, key parameters in the microwave plasma chemical vapor deposition process were precisely controlled and optimized. This ensures that the prepared boron-doped diamond thin film electrode exhibits excellent uniformity, good crystallinity, and controllable boron doping concentration. This not only significantly improves the bonding strength between the film and the porous silicon carbide substrate but also significantly enhances the electrochemical performance of the electrode (such as conductivity, electrocatalytic activity, and stability), achieving efficient and stable preparation of boron-doped diamond thin film electrodes.

[0113] Example 1: 7.5g of silica powder (20nm, 99% purity), 3g of carbon powder (200 mesh, 99% purity), and 3g of aluminum powder (≤25μm, 99% purity) were weighed and initially mixed. The mixture was then added to a ball mill and ball-milled for 6 hours to obtain a uniform powder. 3g of hydroxymethyl cellulose was weighed and dissolved in 3ml of deionized water, with continuous stirring until the hydroxymethyl cellulose was completely dissolved, resulting in a uniform liquid mixture. Subsequently, the pre-prepared powder mixture was slowly poured into the liquid mixture in three portions, with continuous stirring during each pour, until no agglomeration or particles were observed in the mixture, ultimately obtaining a highly uniform colloid mixture.

[0114] In the fabrication of porous SiC substrates, a 50mm*50mm*2mm sheet-like substrate model was designed and imported into a 3D printing machine. The prepared mixed colloid was loaded into the 3D printing inlet to begin printing. The printing speed was set to 10mm / s and the extrusion diameter to 2mm, thus printing a double-layer sheet-like precursor, as shown below. Figure 5 As shown. The printing speed was within the optimized range of 7mm / s-12mm / s, ensuring the quality of the precursor molding. Subsequently, the precursor was left to stand at room temperature for 1 hour, and then transferred to a small box-type drying oven and dried at a drying temperature of 85℃ for 10 hours to obtain a dried double-layer sheet-like precursor preform.

[0115] The dried billet is placed in the constant temperature zone of a tube furnace. After sealing the tube opening, a vacuum is first drawn to 1×10⁻⁶. -2 The pressure was kept below 1000 Pa to thoroughly remove air and impurities from the furnace chamber. Then, 99.999% high-purity argon gas was introduced to atmospheric pressure, maintaining an argon flow rate of 100-150 sccm to maintain a stable inert protective atmosphere. The sintering process was carried out according to the following segmented curves: First, the temperature was increased from room temperature to 1000℃ at a rate of 10℃ / min and held at 1000℃ for 1 hour. This stage mainly served for the decomposition and initial carbonization of the organic binder. Next, the temperature was increased from 1000℃ to 1400℃ at a rate of 10℃ / min and held at 1400℃ for 1 hour. This stage promoted further reaction between carbon and silicon, forming silicon carbide. Finally, the temperature was increased from 1400℃ to 1500℃ at a rate of 5℃ / min and held at 1500℃ for 3 hours. This stage was beneficial for the growth and structural stabilization of silicon carbide grains. After sintering, the substrate was cooled to room temperature in the furnace, resulting in a porous silicon carbide sheet substrate with dimensions of 50mm × 50mm × 2mm. This embodiment successfully prepared a high-purity, structurally uniform porous silicon carbide substrate by precisely controlling the sintering environment and temperature profile, verifying the feasibility of the above technical solution and its effectiveness in improving product quality.

[0116] The prepared porous silicon carbide substrate was placed in a container filled with anhydrous ethanol and ultrasonically cleaned using an ultrasonic cleaning device for 5 minutes. After cleaning, the substrate was removed and dried to remove any residual anhydrous ethanol from the surface.

[0117] Subsequently, the cleaned and dried porous silicon carbide substrate was placed on the sample stage of the microwave plasma chemical vapor deposition system. After closing the cavity, a vacuum treatment was performed on the cavity to achieve a vacuum level of 1×10⁻⁶. -3Next, a preset reaction gas is introduced, for example, methane at a flow rate of 6 sccm and hydrogen at a flow rate of 200 sccm, while diborane at a flow rate of 3 sccm is introduced as the boron source. During deposition, the deposition power is set to 8 kW, the chamber pressure is maintained at 75 Torr, and deposition continues for 4 hours. After deposition, the system is allowed to cool naturally to room temperature, yielding a boron-doped diamond thin film electrode based on a porous silicon carbide substrate.

[0118] Through the above steps, a SiC substrate with a porous structure and a large specific surface area was successfully prepared, such as... Figure 2 As shown, the pore size is 20-30 μm, and interwoven nanowires form between the pores. After deposition, a uniformly distributed C-enriched layer is formed on the surface of the SiC substrate, as shown. Figure 3 As shown in the table, combined with the elemental content comparison data, such as... Figure 4 As shown, the significant increase in carbon content after deposition proves the successful deposition of the BDD film. Based on the pre-deposition ( Figure 2 ) and post-deposition ( Figure 3 The morphological comparison shows that although the number of nanowires decreased significantly after deposition, the number and size of the pores providing the main deposition surface and reaction channels did not change significantly. This electrode structure achieves an exponential increase in reaction area compared to the two-dimensional BDD electrode. This verifies the feasibility of the preparation method of this invention.

[0119] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0120] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a porous silicon carbide substrate boron-doped diamond thin film electrode, characterized in that, The method comprises the steps of: S1. obtaining silica powder, carbon powder and aluminum powder, and mixing the silica powder, carbon powder and aluminum powder to obtain a mixed powder; S2. obtaining a predetermined proportion of hydroxymethyl cellulose and deionized water, diluting the hydroxymethyl cellulose with the deionized water, adding the mixed powder to the diluted hydroxymethyl cellulose to obtain a mixed colloid; S3. according to a predetermined three-dimensional model, using the mixed colloid for three-dimensional printing to obtain a precursor, and drying the precursor to obtain a precursor embryo; S4. sintering the precursor embryo in an inert gas atmosphere to obtain a porous silicon carbide substrate; S5. cleaning the porous silicon carbide substrate and depositing a boron-doped diamond film on the porous silicon carbide substrate to obtain a boron-doped diamond film electrode; Step S1 comprises: Selecting silica powder with a particle size of not more than 20 nm as a silicon source, carbon powder with a fiber size of not more than 200 mesh, and aluminum powder with a particle size of not more than 25 μm, and mixing the silica powder, carbon powder and aluminum powder in a mass ratio of 2.5:1:1, then ball milling for 6-8 h to obtain a mixed powder; Step S3 comprises: According to the predetermined three-dimensional model, the printing path information of the three-dimensional model is determined; According to the printing path information, the printing parameters are adjusted, and the mixed colloid is deposited and formed by using three-dimensional printing technology to obtain a precursor; The precursor is subjected to a standing treatment at room temperature; The precursor after the standing treatment is subjected to a drying treatment to obtain a precursor embryo; Step S4 comprises: Placing the precursor embryo in a tube furnace and vacuumizing to a predetermined range; Introducing argon and sintering in an argon atmosphere to obtain a porous silicon carbide substrate; The step of sintering in stages comprises: Rising from room temperature to 1000℃ at a first predetermined heating rate, and keeping the temperature for 1 h; Rising from 1000℃ to 1400℃ at the first predetermined heating rate, and keeping the temperature for 1 h; Then rising from 1400℃ to 1500℃ at a second predetermined heating rate, keeping the temperature for 3-4 h, and then decreasing to room temperature.

2. The method of claim 1, wherein the porous silicon carbide substrate boron-doped diamond thin film electrode is prepared by the steps of: Step S2 comprises: Obtaining hydroxymethyl cellulose with the same mass as the carbon powder, dissolving it in deionized water in a mass ratio of 1:1, and stirring uniformly to obtain a mixed liquid; Pouring the mixed powder into the mixed liquid and continuously stirring during the pouring process to obtain a uniform mixed colloid.

3. The method of claim 1, wherein the porous silicon carbide substrate boron-doped diamond thin-film electrode is prepared by the steps of: (a) preparing a porous silicon carbide substrate; (b) depositing a boron-doped diamond thin film on the porous silicon carbide substrate; and (c) removing the porous silicon carbide substrate. The step of drying the precursor after the standing treatment to obtain a precursor embryo comprises: Drying the precursor after the standing treatment at a drying temperature of 80-90℃ and a drying time of 5-10 h to obtain a precursor embryo.

4. The method of claim 1, wherein the porous silicon carbide substrate boron-doped diamond thin-film electrode is prepared by the steps of: (a) preparing a porous silicon carbide substrate; (b) depositing a boron-doped diamond thin film on the porous silicon carbide substrate; and (c) annealing the porous silicon carbide substrate boron-doped diamond thin-film electrode. The printing parameters include the jetting speed of the mixed colloid, the printing speed and the layer height of the printing, wherein the jetting speed of the mixed colloid is 7-12 mm / s.

5. The method of claim 1, wherein the porous silicon carbide substrate boron-doped diamond thin-film electrode is prepared by the steps of: (a) preparing a porous silicon carbide substrate; (b) depositing a boron-doped diamond thin film on the porous silicon carbide substrate; and (c) annealing the porous silicon carbide substrate boron-doped diamond thin-film electrode. Step S5 comprises: Cleaning the porous silicon carbide substrate in ultrasonic for 5-10 min with anhydrous ethanol to remove residual substances on the surface of the porous silicon carbide substrate; The cleaned porous silicon carbide substrate is placed in a cavity of a microwave plasma chemical vapor deposition system, and the microwave plasma chemical vapor deposition system deposits a boron-doped diamond film on the porous silicon carbide substrate according to preset parameters, to obtain a boron-doped diamond film electrode.

6. The method of claim 5, wherein the porous silicon carbide substrate boron-doped diamond thin-film electrode is prepared by the steps of: (a) preparing a porous silicon carbide substrate; (b) depositing a boron-doped diamond thin film on the porous silicon carbide substrate; and (c) removing the porous silicon carbide substrate. The preset parameters include: The vacuum of the cavity of the microwave plasma chemical vapor deposition system is reached 1*10 -3 -4*10 -3 Pa; Methane with a flow rate of 6 sccm and hydrogen with a flow rate of 200 sccm are selected as the reaction gas, diborane is selected as the boron source, the flow rate of the diborane is 2 sccm-4 sccm, the deposition power is 8 kW-10 kW, the cavity pressure is 70 Torr-80 Torr, and the deposition duration is 3 h-5 h.

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