A method for preparing a gradient titanium-based boron-doped diamond thin film electrode

Abstract

The application relates to a preparation method of a gradient titanium-based boron-doped diamond thin film electrode and belongs to the technical field of electrode materials. Ti / TiO2 nanotube gradient substrates are obtained by in-situ preparation of TiO2 nanotubes through anodic oxidation of a metal titanium substrate; the Ti / TiO2 nanotube gradient substrates are embedded into carbon powder, high-temperature carbonization treatment is carried out under a protective atmosphere to obtain Ti / TiC nanotube gradient substrates; a boron-doped diamond thin film is deposited onto the surface of the Ti / TiC nanotube gradient substrates by using a chemical vapor deposition method to obtain the gradient titanium-based boron-doped diamond thin film electrode. The TiC nanotubes are synthesized on the titanium substrate in-situ and in advance, the generation of uneven TiC and TiH2 phases in the conventional chemical vapor deposition process can be avoided, an embedded structure is formed between the TiC phase gradient layer and diamond particles, the poor bonding force problem caused by the thermal expansion coefficients and lattice mismatches of various phases is reduced, and the service life of the titanium-based boron-doped diamond thin film electrode is significantly improved.

Description

Technical Field

[0001] This invention relates to a method for preparing a gradient titanium-based boron-doped diamond thin film electrode, belonging to the field of electrode material technology. Background Technology

[0002] Boron-doped diamond electrodes possess characteristics such as a wide potential window, strong chemical stability, corrosion resistance, and resistance to surface contamination. They are widely recognized as one of the anolyte materials with the highest oxygen evolution potential and are considered ideal electrode materials for the electrocatalytic degradation of organic pollutants. They are also widely used in electrocatalytic oxidation, organic electrosynthesis, and electrochemical analysis. The preparation of diamond films requires deposition on a specific substrate using chemical vapor deposition (CVD). Compared to deposition materials such as Si, Ta, and Nb, titanium substrates offer advantages such as superior mechanical properties, high electrical conductivity, and strong corrosion resistance. In particular, their high strength-to-weight ratio, low cost, and strong corrosion resistance make them ideal substrate materials for depositing diamond films. Titanium-based boron-doped diamond film electrodes are expected to become a viable alternative for future industrial applications.

[0003] In actual chemical vapor deposition (CVD) of diamond thin films, the reaction gases within the deposition system include hydrogen, a carbon source (methane or acetone), and a boron source (borane, boric acid, boron trioxide, etc.). Due to the high reactivity of titanium, the hydrogen and carbon sources diffuse into the titanium substrate before diamond film deposition, promoting the formation of TiH2 and porous TiC compounds. The highly conductive TiC phase ensures good conductivity between the titanium substrate and the diamond film. However, the composition control of the TiH2 and TiC phases formed in this process is affected by the specific CVD process, making it difficult to achieve precise control over the composition and thickness uniformity of the intermediate layer. Furthermore, the TiH2 and TiC intermediate layers formed by CVD have low surface roughness and a porous structure, hindering effective bonding between the titanium substrate and the diamond film. Most importantly, the difference in thermal expansion coefficients and lattice mismatch among titanium metal, TiC interlayer, and diamond leads to a decrease in the bonding force between the diamond film and the titanium substrate, significantly reducing the stability of the titanium-based boron-doped diamond film electrode, making the titanium-based boron-doped diamond film prone to peeling off during use. Summary of the Invention

[0004] To address the issue of low lifetime in titanium-based boron-doped diamond films due to differences in composition, thickness, and coefficient of thermal expansion, this invention proposes a method for preparing gradient titanium-based boron-doped diamond film electrodes. The method involves in-situ preparation of TiO2 nanotubes on a titanium substrate via anodic oxidation to obtain a Ti / TiO2 nanotube gradient substrate. This Ti / TiO2 nanotube gradient substrate is then embedded in carbonaceous powder and subjected to high-temperature carbonization under a protective atmosphere to convert TiO2 into a uniformly thick TiC layer with good conductivity, resulting in a Ti / TiC nanotube gradient substrate. Finally, boron-doped diamond films are deposited onto the surface of the Ti / TiC nanotube gradient substrate using chemical vapor deposition (CVD) to obtain the gradient titanium-based boron-doped diamond film electrode. This invention, by pre-synthesizing TiC nanotubes in situ on a titanium substrate, avoids the contact and reaction between the carbon and hydrogen sources and the titanium substrate during conventional CVD, and prevents the generation of inhomogeneous TiC and TiH2 phases in traditional deposition processes, thus achieving the controllable synthesis of highly stable gradient titanium-based boron-doped diamond. The TiC phase gradient layer forms an embedded structure with the diamond particles, which reduces the poor bonding force caused by the thermal expansion coefficients and lattice mismatch of each phase, and significantly improves the service life of titanium-based boron-doped diamond thin film electrodes.

[0005] A method for preparing a gradient titanium-based boron-doped diamond thin film electrode, the specific steps of which are as follows:

[0006] (1) The titanium matrix is ​​treated with NaOH solution, then pretreated with HNO3-HF-H2O solution, and then ultrasonically cleaned with acetone and deionized water to obtain the pretreated titanium matrix; the titanium matrix is ​​a flat plate, porous, network, fiber felt, tubular or irregularly shaped titanium and its alloy materials.

[0007] (2) The pretreated titanium substrate is placed in an acid solution for hydrothermal reaction, so that the surface of the titanium substrate has micro-island and micro-groove structures;

[0008] (3) Using the hydrothermal titanium substrate as the anode and stainless steel, titanium sheet or platinum sheet as the cathode, a DC anodic oxidation reaction is carried out in ethylene glycol-ammonium fluoride-H2O solution to obtain Ti / TiO2 nanotube gradient substrate.

[0009] (4) The Ti / TiO2 nanotube gradient matrix was embedded in carbon powder and subjected to high-temperature carbonization under a protective atmosphere to obtain the Ti / TiC nanotube gradient matrix.

[0010] (5) Boron-doped diamond films were deposited onto the surface of a Ti / TiC nanotube gradient substrate by chemical vapor deposition to obtain a gradient titanium-based boron-doped diamond film electrode.

[0011] In step (1), the NaOH solution has a mass concentration of 10-50%, the alkali treatment temperature is 20-90℃, and the time is 10-90 min; the HNO3-HF-H2O solution has a HNO3 mass concentration of 2-10%, an HF mass concentration of 5-30%, a pretreatment temperature of 10-50℃, and a time of 3-10 min.

[0012] In step (2), the acid solution is an HCl solution, an H2SO4 solution, or a mixed HCl-H2SO4 acid solution. The mass concentration of the HCl solution is 3-17%, the mass concentration of the H2SO4 solution is 10-48%, and the mass concentration of HCl in the mixed HCl-H2SO4 acid solution is 2-15% and the mass concentration of H2SO4 is 5-40%. The hydrothermal reaction temperature is 80-120℃ and the time is 1-4h.

[0013] In step (3), the mass concentration of ammonium fluoride in the ethylene glycol-ammonium fluoride-H2O solution is 0.2-1.0%, and the mass concentration of H2O is 0.5-5.0%.

[0014] The voltage of the DC anodic oxidation reaction in step (3) is 30-60V, the time is 0.5-4h, and the thickness of the TiO2 nanotube is 1-50μm.

[0015] The carbon powder in step (4) is one or more of graphite, coke, carbon black, and resin carbon, and the high-temperature carbonization treatment temperature is 1000-1800℃ and the time is 4-12h.

[0016] The chemical vapor deposition method in step (5) is hot filament chemical vapor deposition.

[0017] Preferably, the reaction gas in the hot-filament chemical vapor deposition method is a hydrogen-methane mixture with a pressure of 2–10 kPa, a filament temperature of 1600–2200 °C, a Ti / TiC nanotube gradient substrate temperature of 700–850 °C, a deposition time of 3–10 h, a boron doping mass of 0.05%–0.2% in the boron-doped diamond film, and a thickness of 1–10 μm.

[0018] More preferably, the volume fraction of methane in the hydrogen-methane mixture is 1% to 5%.

[0019] The gradient titanium-based boron-doped diamond thin film electrode consists of a titanium substrate, a TiC nanotube intermediate layer, and a boron-doped diamond thin film. The TiC nanotube intermediate layer is obtained by carbonizing TiO2 generated from the anodic oxidation of the titanium substrate at high temperature. The TiC nanotube intermediate layer and the boron-doped diamond thin film form an embedded bond.

[0020] The gradient titanium-based boron-doped diamond thin film electrode is used as an anode for electrocatalytic oxidation mineralization to remove organic pollutants from water.

[0021] The gradient titanium-based boron-doped diamond thin film electrode is used as an electrode material for the electrocatalytic synthesis of organic compounds.

[0022] The beneficial effects of this invention are:

[0023] (1) This invention achieves the controllable synthesis of highly stable gradient titanium-based boron-doped diamond by pre-synthesizing TiC nanotubes in situ on a titanium matrix. The interface between TiC nanotubes and titanium matrix is ​​firmly bonded, and the generation of uneven TiC and TiH2 phases during conventional chemical vapor deposition can be avoided.

[0024] (2) The TiC phase gradient layer of the present invention forms an embedded structure between the diamond particles, which reduces the problem of poor bonding force caused by the thermal expansion coefficient and lattice mismatch of each phase, and significantly improves the service life of titanium-based boron-doped diamond thin film electrode. Attached Figure Description

[0025] Figure 1 This is a SEM image of the gradient matrix of flat Ti / TiO2 nanotubes in Example 1;

[0026] Figure 2 This is a SEM image of the boron-doped diamond film from Example 2;

[0027] Figure 3 The cyclic voltammetry curves of the gradient titanium-based boron-doped diamond thin film electrode in 0.5 M sulfuric acid in Example 2 are shown.

[0028] Figure 4 The XRD pattern of the Ti / TiC nanotube gradient matrix in Example 3 is shown.

[0029] Figure 5 SEM image (50kx) of the fiber Ti / TiC nanotube gradient matrix in Example 4;

[0030] Figure 6 SEM image (30kx) of the fiber Ti / TiC nanotube gradient matrix in Example 4;

[0031] Figure 7 The graph shows the accelerated lifetime comparison of boron-doped diamond electrodes in Examples 1 and 4 containing a titanium-based gradient TiC interlayer and the comparative example without a TiC interlayer. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0033] Example 1: A method for preparing a gradient titanium-based boron-doped diamond thin film electrode, the specific steps of which are as follows:

[0034] (1) A flat titanium substrate was placed in a NaOH solution (12% by mass) at 80°C for alkali treatment for 20 min, and then placed in an HNO3-HF-H2O solution for pretreatment at 30°C for 5 min to remove surface oxides and impurities. The substrate was then ultrasonically cleaned with acetone and deionized water for 15 min to obtain a pretreated flat titanium substrate. The HNO3-HF-H2O solution contained 10% HNO3 and 15% HF by mass.

[0035] (2) The pretreated flat titanium substrate was placed in a 17% HCl solution and hydrothermally reacted at 90°C for 60 min to give the surface of the titanium substrate a micro-island and micro-groove structure.

[0036] (3) Using the hydrothermal-reacted flat titanium substrate as the anode and stainless steel as the cathode, a DC anodizing reaction was carried out in an ethylene glycol-ammonium fluoride-H2O solution for 60 min to obtain a flat Ti / TiO2 nanotube gradient substrate; the ethylene glycol mass concentration in the ethylene glycol-ammonium fluoride-H2O solution was 98%, the ammonium fluoride mass concentration was 0.5%, and the H2O mass concentration was 1.5%; the voltage of the DC anodizing reaction was 50V; the thickness of the TiO2 nanotubes in this embodiment was approximately 30μm;

[0037] The SEM image of the flat Ti / TiO2 nanotube gradient matrix in this embodiment is shown below. Figure 1 ,from Figure 1 It can be seen that after the anodizing process, uniform TiO2 nanotubes are formed on the surface of the titanium substrate, and the diameter of the nanotubes is about 100 nm.

[0038] (4) The flat Ti / TiO2 nanotube gradient matrix was embedded in carbon black powder and subjected to high-temperature carbonization treatment at 1200℃ for 2h under a protective atmosphere (Ar) to convert TiO2 into a uniformly thick TiC layer with good conductivity to obtain a Ti / TiC nanotube gradient matrix.

[0039] (5) Boron-doped diamond films were deposited onto the surface of a Ti / TiC nanotube gradient substrate using hot-wire chemical vapor deposition to obtain a gradient titanium-based boron-doped diamond film electrode. The reaction gas in the hot-wire chemical vapor deposition method was a hydrogen-methane mixture (methane volume fraction of 1%), the pressure was 3 kPa, the filament temperature was 2000℃, the Ti / TiC nanotube gradient substrate temperature was 750℃, the deposition time was 8 h, and the flow rate of trimethyl borate was controlled so that the boron doping mass in the boron-doped diamond film was 0.1%.

[0040] In this embodiment, the boron-doped diamond thin-film electrode based on gradient titanium exhibits tightly packed, continuous, and uniformly sized grains of 1–2 μm, with a diamond film thickness of approximately 5 μm. The oxygen evolution potential of the electrode is approximately 2.35 V. Using this electrode as the anode and stainless steel as the cathode, the electrode achieves an oxygen evolution potential of 1 A / cm² in a 1.0 M H₂SO₄ solution. 2 The accelerated lifetime at current density is 347 hours.

[0041] Example 2: A method for preparing a gradient titanium-based boron-doped diamond thin film electrode, the specific steps of which are as follows:

[0042] (1) A flat titanium substrate was treated with NaOH solution (15% by mass) at 60℃ for 30 min, and then pretreated in HNO3-HF-H2O solution at 45℃ for 8 min to remove surface oxides and impurities. The substrate was then ultrasonically cleaned with acetone and deionized water for 20 min to obtain a pretreated flat titanium substrate. The HNO3-HF-H2O solution contained 8% HNO3 and 15% HF by mass.

[0043] (2) The pretreated flat titanium substrate was placed in a 26% H2SO4 solution and hydrothermally reacted at 80°C for 90 min to give the surface of the titanium substrate a micro-island and micro-groove structure.

[0044] (3) Using the hydrothermal-reacted flat titanium substrate as the anode and stainless steel as the cathode, a DC anodizing reaction was carried out in an ethylene glycol-ammonium fluoride-H2O solution for 45 min to obtain a flat Ti / TiO2 nanotube gradient substrate; the ethylene glycol mass concentration in the ethylene glycol-ammonium fluoride-H2O solution was 97%, the ammonium fluoride mass concentration was 0.5%, and the H2O mass concentration was 2.5%; the voltage of the DC anodizing reaction was 60V; the thickness of the TiO2 nanotubes in this embodiment was approximately 40μm;

[0045] (4) The flat Ti / TiO2 nanotube gradient matrix was embedded in carbon black powder and subjected to high-temperature carbonization treatment at 1300℃ for 3h under a protective atmosphere (Ar) to convert TiO2 into a uniformly thick TiC layer with good conductivity to obtain a Ti / TiC nanotube gradient matrix.

[0046] (5) Boron-doped diamond films were deposited onto the surface of a Ti / TiC nanotube gradient substrate using hot-wire chemical vapor deposition to obtain a gradient titanium-based boron-doped diamond film electrode. The reaction gas in the hot-wire chemical vapor deposition method was a hydrogen-methane mixture (methane volume fraction of 1%), the pressure was 4 kPa, the filament temperature was 2000℃, the Ti / TiC nanotube gradient substrate temperature was 750℃, the deposition time was 6 h, and the flow rate of trimethyl borate was controlled so that the boron doping mass in the boron-doped diamond film was 0.13%.

[0047] The SEM image of the boron-doped diamond film in this embodiment is shown below. Figure 2 ,from Figure 2 It can be seen that diamond particles with a grain size of 1 to 2 μm can be obtained by vapor deposition, with good intergranular bonding and high crystallinity;

[0048] In this embodiment, the boron-doped diamond thin-film electrode based on gradient titanium exhibits tightly packed, continuous, and uniformly sized grains of 1–2 μm, with a diamond film thickness of approximately 4 μm. The oxygen evolution potential of the electrode is approximately 2.32 V. Using this electrode as the anode and stainless steel as the cathode, the electrode achieves an oxygen evolution potential of 1 A / cm² in a 1.0 M H₂SO₄ solution. 2 The accelerated lifetime at current density is 326 hours;

[0049] Cyclic voltammetry curves in 0.5 M sulfuric acid using a gradient titanium-based boron-doped diamond thin-film electrode as the anode and stainless steel as the cathode are shown below. Figure 3 ,from Figure 3 It is known that the oxygen evolution potential of the titanium-based boron-doped diamond electrode is about 2.32V, the hydrogen evolution potential is -1.1V, and the potential range is high, reaching 3.4V. At the same time, the boron-doped diamond electrode exhibits a low background current, making it an ideal electrode material for electrocatalysis of organic pollutants and organic electrosynthesis.

[0050] Example 3: A method for preparing a gradient titanium-based boron-doped diamond thin film electrode, the specific steps of which are as follows:

[0051] (1) The fiber titanium felt matrix was alkali-treated in a NaOH solution (mass concentration of 10%) at 60℃ for 15 min, and then placed in an HNO3-HF-H2O solution for pretreatment at 25℃ for 5 min to remove surface oxides and impurities. It was then ultrasonically cleaned with acetone and deionized water for 25 min in sequence to obtain a pretreated metallic titanium matrix. The HNO3-HF-H2O solution contained 10% HNO3 and 30% HF.

[0052] (2) The pretreated titanium substrate is placed in a HCl-H2SO4 mixed solution and hydrothermally reacted at 100℃ for 90 min to give the surface of the titanium substrate a micro-island and micro-groove structure; the mass concentration of HCl in the HCl-H2SO4 mixed solution is 10% and the mass concentration of H2SO4 is 15%.

[0053] (3) Using the hydrothermal titanium substrate as the anode and stainless steel as the cathode, a direct current anodizing reaction was carried out in an ethylene glycol-ammonium fluoride-H2O solution for 30 min to obtain a Ti / TiO2 nanotube gradient substrate; the ethylene glycol mass concentration in the ethylene glycol-ammonium fluoride-H2O solution was 98%, the ammonium fluoride mass concentration was 0.8%, and the H2O mass concentration was 1.2%; the voltage of the direct current anodizing reaction was 50V; the thickness of the TiO2 nanotubes in this embodiment was approximately 27μm;

[0054] (4) The Ti / TiO2 nanotube gradient matrix was embedded in carbon powder and subjected to high-temperature carbonization treatment at 1000℃ for 8h under a protective atmosphere (Ar) to convert TiO2 into a uniformly thick TiC layer with good conductivity to obtain the Ti / TiC nanotube gradient matrix.

[0055] The XRD pattern of the Ti / TiC nanotube gradient matrix in this embodiment is shown below. Figure 4 ,from Figure 4 It can be seen that, in addition to the diffraction peaks of the titanium matrix, there are also obvious TiC diffraction peaks in the XRD pattern, indicating that TiO2 can be converted into the TiC phase through high-temperature carbonization reaction;

[0056] (5) Boron-doped diamond films were deposited onto the surface of a Ti / TiC nanotube gradient substrate using hot-wire chemical vapor deposition to obtain a gradient titanium-based boron-doped diamond film electrode. The reaction gas in the hot-wire chemical vapor deposition method was a hydrogen-methane mixture (methane volume fraction of 2%), the pressure was 3 kPa, the filament temperature was 2000℃, the Ti / TiC nanotube gradient substrate temperature was 750℃, the deposition time was 8 h, and the flow rate of trimethyl borate was controlled so that the boron doping mass in the boron-doped diamond film was 0.1%.

[0057] In this embodiment, the boron-doped diamond thin-film electrode based on gradient titanium exhibits tightly packed, continuous, and uniformly sized grains, with a grain size of 0.5–1 μm and a diamond film thickness of approximately 3 μm. The electrode has an oxygen evolution potential of approximately 2.27 V. Using this electrode as the anode and stainless steel as the cathode, the electrode achieves an oxygen evolution potential of 1 A / cm² in a 1.0 M H₂SO₄ solution. 2 The accelerated lifetime at current density is 279 hours.

[0058] Example 4: A method for preparing a gradient titanium-based boron-doped diamond thin film electrode, the specific steps of which are as follows:

[0059] (1) The fiber titanium felt matrix was alkali-treated in a NaOH solution (mass concentration of 10%) at 40℃ for 30 min, and then placed in an HNO3-HF-H2O solution for pretreatment at 30℃ for 5 min to remove surface oxides and impurities. It was then ultrasonically cleaned with acetone and deionized water for 15 min to obtain the pretreated metallic titanium matrix. The HNO3-HF-H2O solution contained 4% HNO3 and 15% HF.

[0060] (2) The pretreated titanium substrate was placed in a HCl-H2SO4 mixed solution and hydrothermally reacted at 110°C for 60 min to give the surface of the titanium substrate a micro-island and micro-groove structure; the mass concentration of HCl in the HCl-H2SO4 mixed solution was 9% and the mass concentration of H2SO4 was 12%.

[0061] (3) Using the hydrothermal titanium substrate as the anode and stainless steel as the cathode, a DC anodizing reaction was carried out in an ethylene glycol-ammonium fluoride-H2O solution for 60 min to obtain a Ti / TiO2 nanotube gradient matrix; the mass concentration of ethylene glycol in the ethylene glycol-ammonium fluoride-H2O solution was 98.0%, the mass concentration of ammonium fluoride was 1.0%, and the mass concentration of H2O was 1.0%; the voltage of the DC anodizing reaction was 60V; the thickness of the TiO2 nanotubes in this embodiment was approximately 45μm;

[0062] (4) The Ti / TiO2 nanotube gradient matrix was embedded in carbon powder and subjected to high-temperature carbonization treatment at 1200℃ for 4h under a protective atmosphere (Ar) to convert TiO2 into a uniformly thick TiC layer with good conductivity to obtain the Ti / TiC nanotube gradient matrix.

[0063] The SEM image of the fibrous Ti / TiC nanotube gradient matrix in this embodiment is shown below. Figures 5-6 ,from Figures 5-6 It can be seen that after the anodizing process, uniform TiO2 nanotubes are formed on the surface of the fiber titanium felt matrix. The diameter of the nanotubes is about 100nm, and the entire matrix still maintains a complete fibrous structure.

[0064] (5) Boron-doped diamond films were deposited onto the surface of a Ti / TiC nanotube gradient substrate using hot-wire chemical vapor deposition to obtain a gradient titanium-based boron-doped diamond film electrode. The reaction gas in the hot-wire chemical vapor deposition method was a hydrogen-methane mixture (methane volume fraction of 1%), the pressure was 3 kPa, the filament temperature was 2000℃, the Ti / TiC nanotube gradient substrate temperature was 750℃, the deposition time was 8 h, and the flow rate of trimethyl borate was controlled so that the boron doping mass in the boron-doped diamond film was 0.1%.

[0065] In this embodiment, the boron-doped diamond thin-film electrode based on gradient titanium exhibits tightly packed, continuous, and uniformly sized grains of 1–2 μm, with a diamond film thickness of approximately 5 μm. The oxygen evolution potential of the electrode is approximately 2.42 V. Using this electrode as the anode and stainless steel as the cathode, the electrode achieves an oxygen evolution potential of 1 A / cm² in a 1.0 M H₂SO₄ solution. 2 The accelerated lifetime at current density is 435 hours.

[0066] Comparative Example: In this comparative example, boron-doped diamond thin film was deposited on the pretreated titanium substrate of Example 4 by hot-wire chemical vapor deposition to obtain a titanium-based boron-doped diamond thin film electrode.

[0067] Using boron-doped diamond electrodes containing a titanium-based gradient TiC interlayer in Examples 1 and 4, and a comparative example without a TiC interlayer, as anodes and stainless steel as cathodes, respectively, in 1.0 M H₂SO₄ solution, the electrode concentration was 1 A / cm². 2 Accelerated lifetime testing at current density;

[0068] The accelerated lifetime comparison graphs of boron-doped diamond electrodes containing titanium-based gradient TiC interlayers in Examples 1 and 4, and those without TiC interlayers in the comparative example, are shown below. Figure 7 ,from Figure 7 It can be seen that the accelerated lifetime of the fiber titanium felt-based boron-doped diamond thin film electrode with gradient TiC interlayer in Example 4 is 435h, the accelerated lifetime of the planar titanium-based boron-doped diamond thin film electrode with gradient TiC interlayer in Example 1 is 347h, while the accelerated lifetime of the boron-doped diamond electrode without TiC interlayer is only 224h, which proves the effect of gradient TiC interlayer on improving the stability of titanium-based boron-doped diamond.

[0069] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing a gradient titanium-based boron-doped diamond thin film electrode, characterized in that, The specific steps are as follows: (1) The titanium matrix was treated with NaOH solution, then pretreated with HNO3-HF-H2O solution, and then ultrasonically cleaned with acetone and deionized water to obtain the pretreated titanium matrix. (2) The pretreated titanium matrix is ​​placed in an acid solution for hydrothermal reaction; the acid solution is HCl solution, H2SO4 solution or HCl-H2SO4 mixed acid solution, the mass concentration of HCl solution is 3~17%, the mass concentration of H2SO4 solution is 10~48%, the mass concentration of HCl in HCl-H2SO4 mixed acid solution is 2~15%, and the mass concentration of H2SO4 is 5~40%; the hydrothermal reaction temperature is 80~120℃, and the time is 1~4h; (3) Using the hydrothermal titanium substrate as the anode and stainless steel, titanium sheet or platinum sheet as the cathode, a DC anodic oxidation reaction is carried out in ethylene glycol-ammonium fluoride-H2O solution to obtain a Ti / TiO2 nanotube gradient substrate; (4) The Ti / TiO2 nanotube gradient matrix is ​​embedded in carbon powder and subjected to high-temperature carbonization treatment under a protective atmosphere to obtain the Ti / TiC nanotube gradient matrix; the carbon powder is one or more of graphite, coke, carbon black, and resin carbon, and the high-temperature carbonization treatment temperature is 1000~1800℃ and the time is 4~12h. (5) Boron-doped diamond films are deposited on the surface of Ti / TiC nanotube gradient substrates using chemical vapor deposition to obtain gradient titanium-based boron-doped diamond film electrodes; the chemical vapor deposition method is hot-wire chemical vapor deposition, the reaction gas of hot-wire chemical vapor deposition is a hydrogen-methane mixture, the pressure is 2~10 kPa, the filament temperature is 1600~2200℃, the temperature of Ti / TiC nanotube gradient substrate is 700~850℃, the deposition time is 3~10h, the boron doping mass in the boron-doped diamond film is 0.05%~0.2%, and the thickness of the boron-doped diamond film is 1~10μm.

2. The method for preparing the gradient titanium-based boron-doped diamond thin film electrode according to claim 1, characterized in that: Step (1) The mass concentration of NaOH solution is 10~50%, the alkali treatment temperature is 20~90℃, and the time is 10~90min; the mass concentration of HNO3 in HNO3-HF-H2O solution is 2~10%, the mass concentration of HF is 5~30%, the pretreatment temperature is 10~50℃, and the time is 3~10min.

3. The method for preparing a gradient titanium-based boron-doped diamond thin film electrode according to claim 1, characterized in that: In step (3), the mass concentration of ammonium fluoride in the ethylene glycol-ammonium fluoride-H2O solution is 0.2~1.0%, and the mass concentration of H2O is 0.5~5.0%.

4. The method of claim 1, wherein the gradient titanium-based boron-doped diamond thin film electrode is prepared by the steps of: Step (3) The voltage of the DC anodizing reaction is 30~60V, the time is 0.5~4h, and the thickness of the TiO2 nanotube is 1~50μm. ​ 5. The method for preparing a gradient titanium-based boron-doped diamond thin film electrode according to claim 1, characterized in that: The volume fraction of methane in the hydrogen-methane mixture is 1% to 5%.

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