BDD electrode and preparation method and application thereof

Abstract

The invention discloses a BDD electrode and a preparation method and application thereof. The preparation method of the BDD electrode comprises the following steps that S1, electroplating is conducted, specifically, a foam metal material serves as a cathode, and a Ni-W alloy layer is formed on the surface of the cathode through electroplating; s2, heat treatment is conducted, specifically, the cathode treated in the step S1 is subjected to annealing treatment at the temperature of 400-500 DEG C in the inert atmosphere; s3, surface treatment is conducted, specifically, after the cathode treated in the step S2 is cooled, mechanical treatment is conducted on the Ni-W alloy layer through a first grinding material and a second grinding material in sequence; and S4, deposition: depositing a boron-doped diamond layer on the surface of the cathode treated in the step S3 through hot filament chemical vapor deposition. According to the prepared electrode, compact and uniform boron-doped diamond film growth is achieved on the foam metal material substrate, and the electrode shows excellent conductivity and long-term stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrocatalysis, and in particular to a boron-doped diamond (BDD) electrode and a preparation method and application thereof. BACKGROUND

[0002] As a new type of functional material, the boron-doped diamond (BDD) electrode has shown important application value in environmental governance, energy conversion and biosensing, etc. due to its excellent electrochemical performance (including high electrical conductivity, strong chemical stability and wide potential window characteristics). In the scenes of electrocatalytic degradation, organic pollutant treatment and electrochemical detection, the redox efficiency and reaction selectivity of the BDD electrode are significantly better than those of traditional electrode materials.

[0003] In the prior art, the BDD electrode is mostly made of dense planar materials such as silicon (Si) and titanium (Ti) as a substrate. However, the three-dimensional structural defects of such a substrate limit the specific surface area of the electrode, and the mass transfer efficiency is difficult to meet the demand of high load working conditions, which restricts the practical application of the BDD electrode in scenes requiring high current density or rapid mass transfer.

[0004] In recent years, the foam metal material (such as foam copper and foam copper-nickel) with a three-dimensional porous structure is considered as an ideal choice for constructing a high-performance electrode carrier due to its high specific surface area and low resistance characteristics. However, the traditional BDD preparation method mainly adopts the high-temperature chemical vapor deposition method (CVD), which has strict requirements for the substrate. The foam metal material faces severe challenges in the high-temperature CVD environment: 1) insufficient temperature resistance: the CVD process is usually carried out at high temperature, and many foam metals are prone to softening, deformation, grain coarsening or even melting at this temperature, which leads to the collapse or serious degradation of the three-dimensional porous structure and the loss of its core advantages; 2) poor surface stability: at high temperature, the surface of the foam metal is easily oxidized, corroded or reacted with the reaction gas, forming a non-diamond carbon phase (such as graphite and amorphous carbon) or a metal carbide layer. Such a "contamination layer" will seriously hinder the direct nucleation and growth of high-quality BDD films.

[0005] Therefore, it is of great significance to design a new process to prepare a BDD electrode with good temperature resistance and surface stability. SUMMARY

[0006] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application proposes a preparation method of a BDD electrode, and the electrode prepared by the method has good temperature resistance and surface stability.

[0007] The present application also proposes a BDD electrode prepared by the above preparation method.

[0008] The present application also proposes the application of the above BDD electrode.

[0009] According to an aspect of the present application, a preparation method of a BDD electrode is provided, comprising the following steps: S1, electroplating: taking a foamed metal material as a cathode, forming a Ni-W alloy layer on the surface of the cathode by electroplating; S2, heat treatment: annealing the cathode after step S1 in an inert atmosphere at 400-500℃; S3, surface treatment: after the cathode after step S2 is cooled, mechanically treating the Ni-W alloy layer with a first abrasive and a second abrasive in sequence; wherein the first abrasive and the second abrasive both contain diamond and the average particle size of the diamond in the first abrasive is greater than that in the second abrasive; S4, deposition: depositing a boron-doped diamond layer on the surface of the cathode after step S3 by hot wire chemical vapor deposition.

[0010] The preparation method of the BDD electrode according to the embodiment of the present application has at least the following beneficial effects: the electrode prepared by the present application realizes the growth of a dense and uniform boron-doped diamond (BDD) film on a foam metal material substrate, and the electrode exhibits excellent electrical conductivity and long-term stability. The mechanism of the preparation method of the present application includes the following: first, a transition conductive layer is constructed on the surface of the foam copper-nickel substrate by Ni-W alloy electroplating. The plating layer has a dual function: (1) significantly improving the thermal stability and corrosion resistance of the substrate; (2) as an intermediate layer, effectively enhancing the interfacial adhesion between the BDD film and the porous substrate. Subsequently, the surface of the Ni-W alloy layer is optimized: a mechanical grinding process using double-sized diamond powder is adopted to construct a composite rough structure of different scales on the surface. This process not only provides the physical anchoring points (multi-level roughness) required for diamond heterogeneous nucleation, but also provides abundant carbon "seeds" through the inlaid diamond particles, thereby synergistically promoting the uniformity and density of diamond nucleation. Compared with ion etching or chemical etching, this mechanical treatment process has the advantages of low processing difficulty, high efficiency, and low risk of damage to the foam metal substrate while achieving equivalent surface functions (multi-level roughness and nucleation points); compared with traditional roughening processes such as sandblasting, it has the dual advantages of fine control of surface topography and direct provision of carbon sources. Further, the present application anneals the Ni-W alloy layer at 400-500°C. This temperature range design takes into account: (1) enhancing the density and structural stability of the Ni-W layer; (2) optimizing the surface microcrystalline arrangement, which is beneficial to subsequent uniform diamond nucleation; (3) avoiding damage to the foam copper-nickel substrate at high temperatures. The entire process flow is as follows: three-dimensional porous foam substrate → Ni-W alloy electroplating (forming a transition layer) → low-temperature annealing (optimizing the transition layer) → double-sized diamond powder mechanical grinding (surface roughening and pre-planting of carbon seeds) → BDD deposition. Finally, a high specific surface area electrode with a dense and uniform BDD film and strong adhesion is successfully constructed on the complex three-dimensional porous structure. This structure has great potential in high-efficiency electrochemical applications such as electrocatalysis, electroanalysis, and electrochemical oxidation. In addition, the preparation method has a relatively simple process and controllable cost, and has good prospects for large-scale production.

[0011] According to some embodiments of the present application, the foam metal material comprises a foam metal or alloy.

[0012] According to some embodiments of the present application, the foam metal material is selected from at least one of a foam copper, a foam nickel, a foam titanium, a foam niobium, a foam iron-nickel, or a foam copper-nickel.

[0013] According to some embodiments of the present application, the electroplating conditions in step S1 include at least one of the following conditions: 1) the electroplating solution comprises Ni 2+ salt, tungstate, complexing agent, and ammonium chloride; 2) pH of the plating solution is 7-9; 3) Temperature is 50-70℃; 4) Current density is 1-5 A / dm 2 ; 5) Time is 10-30 min.

[0014] According to some embodiments of the present application, the complexing agent comprises at least one of citrate, ethylenediaminetetraacetate, tartrate and gluconate. The addition of complexing agents such as citrate can form soluble complexes with Ni 2+ and WO4 2- to stabilize the tungsten source.

[0015] According to some embodiments of the present application, the plating solution further comprises at least one of ammonium sulfate, ammonium acetate, sodium chloride or potassium chloride. Other ingredients providing ammonium ions or chloride ions can also be added to improve conductivity and ammonium ions, reduce cathode polarization, improve current efficiency and improve deposition uniformity.

[0016] According to some embodiments of the present application, the plating solution comprises the following components: NiSO4·6H2O: 180-420 g / L; Na2WO4·2H2O: 45-110 g / L; Na3C6H5O7 (sodium citrate): 35-85 g / L; NH4Cl: 25-55 g / L.

[0017] According to some embodiments of the present application, the pH of the plating solution is adjusted by ammonia.

[0018] According to some embodiments of the present application, the thickness of the Ni-W alloy layer formed in step S1 is 1-10 μm.

[0019] According to some embodiments of the present application, the annealing treatment time in step S2 is 30-60 min.

[0020] According to some embodiments of the present application, the foam metal material is pretreated before plating, and the pretreatment step comprises acid immersion treatment. The oxide layer is removed and the surface is chemically activated by acid immersion.

[0021] According to some embodiments of the present application, the pretreatment further comprises a cleaning step before acid immersion, and the cleaning can be performed in an ultrasonic bath using ethanol and / or water as the cleaning medium. The physical contaminants such as oil stains on the surface are removed by ultrasonic cleaning.

[0022] According to some embodiments of the present application, the pretreatment further comprises a rinsing step after acid immersion, and the rinsing can be performed using water.

[0023] According to some embodiments of the present application, the pre-treatment further comprises a drying step after rinsing, which can be achieved by drying or the like.

[0024] According to some embodiments of the present application, the anode in the electroplating process is Ni or stainless steel.

[0025] According to some embodiments of the present application, the inert atmosphere is an inert gas atmosphere or a nitrogen atmosphere.

[0026] According to some embodiments of the present application, the cooling is achieved by natural cooling. The slow cooling is achieved by natural cooling.

[0027] According to some embodiments of the present application, the first abrasive and the second abrasive are respectively mixed with diamond in a mass ratio of 0.5-2%.

[0028] According to some embodiments of the present application, the average particle size of the diamond in the first abrasive is 0.1-2 μm.

[0029] According to some embodiments of the present application, the average particle size of the diamond in the second abrasive is 50-100 nm. The average particle sizes of the diamond in the first abrasive and the second abrasive are not both 100 nm.

[0030] According to some embodiments of the present application, the mass ratio of the diamond in the first abrasive to the diamond in the second abrasive is 1:5 to 5:1.

[0031] The Ni-W surface is polished twice with large and small particle size diamond, which enhances the diamond nucleation ability and improves the film adhesion.

[0032] According to some embodiments of the present application, the deposition conditions include: hot wire temperature: 2100-2300 ℃, substrate temperature: 650-750 ℃, atmosphere: mixed atmosphere containing CH4 and H2, and boron source is added as a doping source. In the hot filament chemical vapor deposition (HFCVD) process of the present application, the use of high temperature hot wire is the key to achieve efficient diamond film growth. Its core function is to provide sufficient energy to promote efficient thermal cracking of gas-phase carbon sources (such as methane) to generate high concentrations of active carbon-containing groups (such as CH3•, C2H2, H•, etc.) and atomic carbon. These active species are the material basis for diamond nucleation and growth.

[0033] The present application adopts a hot wire temperature significantly higher than the conventional one (>2100℃), which has the following advantages compared with the conventional process (800-1000℃): 1. Enhanced carbon source cracking efficiency: higher hot wire temperature can more thoroughly break the C-H bond of methane molecules, significantly increasing the generation rate and concentration of active carbon-containing groups, providing sufficient carbon source supply for rapid and high-density nucleation of diamond; 2. Promote the formation of dense film layer: high concentration of active carbon species is conducive to the rapid formation of a large number of diamond crystal nuclei on the substrate surface and supports their subsequent dense growth, thereby obtaining high-quality, low-porosity diamond films in a shorter time; 3. Optimize foam substrate deposition: for foam copper-nickel substrates with complex three-dimensional porous structures: the high-temperature environment (radiation from the hot wire and convective transfer of the reaction gas) helps maintain the thermal stability of the substrate during deposition (provided that the overall deposition temperature is controlled within the substrate's tolerance range). High temperature promotes the sufficient diffusion and penetration of active carbon species inside the foam pores, ensuring uniform coverage of the diamond film. While conventional hot wire temperatures (such as 800-1000℃) may result in insufficient methane cracking, insufficient concentration of active carbon species, and thus slow nucleation rate and low nucleation density, the growth process may be more prone to forming coarse-grained, non-dense, or even discontinuous film layers, affecting the quality and performance of the final film.

[0034] In summary, the present application solves the key problems of insufficient active carbon source supply and low nucleation density in diamond CVD by using a high-temperature hot wire, enabling efficient deposition of dense, uniform, and well-adhered high-quality diamond films on three-dimensional porous foam copper-nickel substrates.

[0035] According to some embodiments of the present application, the volume ratio of methane to hydrogen during the deposition process is 10:500-30:500.

[0036] According to some embodiments of the present application, the volume ratio of methane to hydrogen during the deposition process is 20:500.

[0037] According to some embodiments of the present application, the boron source is a gaseous, liquid, or solid boron source, and the liquid or solid boron source is doped in the working atmosphere of the deposition process after vaporization.

[0038] According to some embodiments of the present application, the boron source is added in an amount of 1%~5% of the volume flow rate of methane gas.

[0039] According to some embodiments of the present application, the boron source includes at least one of B(OCH3)3, diborane, diborane, boron trifluoride, and trimethylboron.

[0040] According to some embodiments of the present application, the boron source includes a gaseous boron source. The use of a gaseous boron source makes the doping more uniform.

[0041] According to some embodiments of the present application, the deposition conditions further include: pressure: 3-10 Torr, deposition time: 5-10 hours.

[0042] According to another aspect of the present application, there is provided a BDD electrode prepared by the above method.

[0043] According to another aspect of the present application, there is provided a BDD electrode prepared by the above method.

[0044] According to another aspect of the present application, there is provided a BDD electrode prepared by the above method.

[0045] Additional aspects and advantages of the present application will be given in part in the following description, become apparent from the following description, or be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a scanning electron microscope (SEM) image of the foam copper-nickel used as the substrate in the examples and comparative examples of the present application.

[0047] Figure 2 is an SEM image of the surface of the cathode after grinding in Example 1 of the present application.

[0048] Figure 3 is a wide-field SEM image of the surface of the cathode after grinding in Example 1 of the present application.

[0049] Figure 4 is an SEM image of the BDD film formed in Example 1 of the present application.

[0050] Figure 5 is a Raman spectrum of the BDD electrode prepared in Example 1 of the present application.

[0051] Figure 6 is a graph of the results of the electrochemical stability test of the BDD electrodes prepared in Example 1 and Comparative Examples 1-4 of the present application. DETAILED DESCRIPTION

[0052] The concept and the technical effects of the present application will be described clearly and completely in combination with the embodiments. It is obvious that the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present application. The test methods used in the embodiments are conventional methods unless otherwise specified. The materials and reagents used are commercially available unless otherwise specified. The same parameters are used in the same way in the embodiments unless otherwise specified. The following described embodiments are exemplary and are used to explain the present application, but cannot be understood as limiting the present application.

[0053] In the description of the present application, the description of the terms "some embodiments" and the like means that the specific features, structures, materials or characteristics described in combination with the embodiments or examples are contained in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0054] In the description of the present application, if the first, second, etc. are described, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0055] Example 1 This example provides a BDD electrode, which is prepared by the following steps: (1) Cleaning and activation treatment of foamed copper-nickel: foamed copper-nickel (pore ratio about 85%, block shape) is cut into small samples of 10 mm x 10 mm x 2 mm. Ultrasonic cleaning (ethanol, water each for 10 min), immersion in dilute hydrochloric acid (10 wt%) for 2 min to remove the oxide layer, and washing with deionized water for 3 times, drying at 70°C for 30 min, and standby.

[0056] (2) Ni-W alloy electroplating on the surface thereof; the electroplating process conditions are as follows: Electrolyte composition: NiSO4·6H2O: 300 g / L, Na2WO4·2H2O: 80 g / L, Na3C6H5O7 (sodium citrate): 60 g / L, NH4Cl: 50 g / L. Adjust pH to 8 (with ammonia water), electroplating temperature 60°C, anode Ni, current density 3 A / dm 2 , time 20 min, to obtain a Ni-W alloy layer with a thickness of about 5 μm.

[0057] (3) Annealing at 450℃ for 45 minutes under inert atmosphere (N2) and natural (slow) cooling; annealing to improve the density and thermal stability of the intermediate layer.

[0058] (4) Using diamond powder with an average particle size of 0.5 μm (particle size range 0.3-1.5 μm, hereinafter referred to as coarse particle size) to prepare a 1% by mass suspension (to cover the electrode), using diamond powder with an average particle size of 50 nm (particle size range 20-100 nm, hereinafter referred to as fine particle size) to prepare a 1% by mass suspension (to cover the electrode), and performing double-particle-size polishing (coarse first, then fine) on the Ni-W surface (first, using the suspension containing the coarse particle size diamond powder to polish for 10 minutes, then rinsing with deionized water, ultrasonic treatment for 3 minutes, and drying, then using the suspension containing the fine particle size diamond powder to polish for 10 minutes); through the double-particle-size diamond powder composite treatment of the multi-scale rough structure, the uniformity of nucleation and the film density are enhanced.

[0059] (5) Depositing a BDD film on the surface by hot-wire chemical vapor deposition. The deposition temperature of the BDD film is 700℃, the hot-wire temperature is 2100℃, the working atmosphere is a CH4 and H2 mixed gas (volume ratio 20:500), the mixed gas is doped with vaporized B(OCH3)3 (carrier gas H2 flow rate 0.5 sccm, volume 10% of the flow rate of the methane gas), the pressure is 6 Torr, and the deposition time is 8 hours.

[0060] The obtained electrode has a three-dimensional porous structure and the surface is uniformly covered with a BDD film, has a wide potential window and high stability.

[0061] The microstructure of the foam copper-nickel before treatment was observed by scanning electron microscopy, and the results are shown in Figure 1 From Figure 1 it can be seen that the surface structure of the foam copper-nickel is regular and relatively flat, and the grains are large.

[0062] The cathode after step (4) was characterized by SEM, and the results are shown in Figures 2-3 From Figures 2-3 it can be seen that the surface of the cathode after forming the nickel-tungsten alloy plating layer is rough, the grains are small, and has a more abundant micro-nano structure and a larger specific surface area.

[0063] The BDD electrode after deposition to form a BDD film was characterized by SEM, and the results are shown in Figure 4 From the figure, it can be seen that the electrode surface presents obvious diamond characteristic structure, which is more conducive to improving the electrochemical performance (such as catalytic efficiency and stability, etc.). The prepared BDD electrode was also characterized by Raman spectroscopy, and the results are shown in Figure 5 In the figure, the Raman shift is 1350 cm -1The peak corresponding to diamond (Diamond) peak, 1575 cm -1 The main peak information in the figure is shown in Table 1 below.

[0064] Table 1

[0065] Since the diamond peak and the graphite peak can directly reflect the crystalline quality of the diamond film and the graphite content, other peak intensities are low and are background or impurity peaks, which have little significance for evaluating the film quality, and therefore are not listed.

[0066] From Figure 5 As can be seen from Table 1, the intensity of the diamond peak is significantly higher than that of the graphite peak, and the I 金刚石 / I G of the sample is 37.332, which indicates that the sample is a relatively pure microcrystalline diamond.

[0067] Example 2 This example provides a BDD electrode prepared by the following steps: (1) Cleaning and activation treatment of the foamed nickel: foamed nickel (pore rate about 85%, block shape) is cut into small samples of 10 mm x 10 mm x 2 mm. Ultrasonic cleaning (ethanol, water each for 10 min), immersion in dilute hydrochloric acid (10 wt%) for 2 min to remove the oxide layer, and washing with deionized water for 3 times, drying at 70°C for 30 min, and standby.

[0068] (2) Ni-W alloy electroplating on the surface thereof; the electroplating process conditions are as follows: Electrolyte composition: NiSO4·6H2O: 300 g / L, Na2WO4·2H2O: 70 g / L, EDTA·2Na (ethylenediaminetetraacetic acid disodium): 50 g / L, total mass concentration of ammonium acetate and NH4Cl (molar ratio of 1:2): 35 g / L. Adjust pH to 8 (with ammonia water), electroplating temperature 60°C, anode is Ni, current density 3 A / dm 2 , time 20 min, to obtain a Ni-W alloy layer with a thickness of about 4 μm.

[0069] (3) Annealing at 450°C for 45 minutes under inert atmosphere (N2), and natural (slow) cooling; annealing to improve the density and thermal stability of the intermediate layer.

[0070] (4) Using diamond powder with an average particle size of 1.0 μm (particle size range 0.3-1.5 μm, hereinafter referred to as coarse particle size) to prepare a 1% by mass suspension, and diamond powder with an average particle size of 50 nm (particle size range 20-100 nm, hereinafter referred to as fine particle size) to prepare a 0.5% by mass suspension, to perform double-particle-size polishing (coarse first, fine second, first use the suspension containing coarse particle size diamond powder to polish for 8 min, then rinse with deionized water, ultrasonic for 3 min, dry, then use the suspension containing fine particle size diamond powder to polish for 8 min) on the Ni-W surface; through the double-particle-size diamond powder composite treatment of the multi-scale rough structure, to enhance the nucleation uniformity and film density.

[0071] (5) BDD film is deposited on the surface by hot wire chemical vapor deposition. The deposition temperature of the BDD film is 720°C, the hot wire temperature is 2200°C, the working atmosphere is CH4, H2 mixed gas (volume ratio is 20:500), the mixed gas is doped with trimethylboron (TMB, gas flow is 0.1 sccm, volume is 0.2% of the methane gas flow), the pressure is 6 Torr, and the deposition time is 8 h.

[0072] Example 3 This example provides a BDD electrode, which is prepared by the following steps: (1) The foam copper-nickel is cleaned and activated: the foam copper-nickel (pore ratio about 85%, block shape) is cut into small samples of 10 mm x 10 mm x 2 mm. Ultrasonic cleaning (ethanol, water each for 10 min) is used, and the sample is immersed in dilute hydrochloric acid (10 wt%) for 2 min to remove the oxide layer, and then washed with deionized water for 3 times, and dried at 70°C for 30 min, ready for use.

[0073] (2) Ni-W alloy electroplating is performed on the surface; the electroplating process conditions are as follows: Electrolyte composition: NiSO4·6H2O: 300 g / L, Na2WO4·2H2O: 80 g / L, Na3C6H5O7: 60 g / L, NH4Cl: 35 g / L. The pH is adjusted to 8 (with ammonia water), the electroplating temperature is 60°C, the anode is Ni, the current density is 3 A / dm 2 , and the time is 20 min, to obtain a Ni-W alloy layer with a thickness of about 5 μm.

[0074] (3) Annealing at 450°C for 45 min under inert atmosphere (N2), and natural (slow) cooling; annealing to improve the density and thermal stability of the intermediate layer.

[0075] (4) Using diamond powder with an average particle size of 0.5 μm (particle size range 0.3-1.5 μm, hereinafter referred to as coarse particle size) to prepare a suspension with a mass percentage of 1%, and diamond powder with an average particle size of 50 nm (particle size range 20-100 nm, hereinafter referred to as fine particle size) to prepare a suspension with a mass percentage of 0.8%, to conduct double-particle-size polishing (coarse first, fine second, first use the suspension containing coarse particle size diamond powder to polish for 10 min, then rinse with deionized water, ultrasonic for 3 min, dry, and then use the suspension containing fine particle size diamond powder to polish for 6 min) on the surface of the Ni-W; through the double-particle-size diamond powder composite treatment of the multi-scale rough structure, the uniformity of nucleation and the film densification are enhanced.

[0076] (5) BDD film is deposited on the surface by hot wire chemical vapor deposition. The deposition temperature of the BDD film is 680°C, the hot wire temperature is 2100°C, the working atmosphere is CH4, H2 mixed gas (volume ratio is 25:500), the mixed gas is doped with vaporized (B(OCH3)3) (carrier gas H2 flow is 0.5 sccm, volume is 0.15% of the flow rate of methane gas), the pressure is 5 Torr, and the deposition time is 8 h.

[0077] Example 4 This example provides a BDD electrode prepared by the following steps: (1) The foam copper-nickel is cleaned and activated: the foam copper-nickel (pore rate about 85%, blocky) is cut into small samples of 10 mm x 10 mm x 2 mm. Ultrasonic cleaning (ethanol, water each for 10 min) is adopted, and the oxide layer is removed by soaking in dilute hydrochloric acid (10 wt%) for 2 min, and then washed with deionized water for 3 times, and dried at 70°C for 30 min, ready for use.

[0078] (2) Ni-W alloy electroplating is conducted on the surface; the electroplating process conditions are as follows: Electroplating solution composition: NiSO4·6H2O: 420 g / L, Na2WO4·2H2O: 110 g / L, Na3C6H5O7: 60 g / L, NH4Cl: 35 g / L. The pH is adjusted to 8 (with ammonia water), the electroplating temperature is 60°C, the anode is Ni, the current density is 3 A / dm 2 , the time is 20 min, and a Ni-W alloy layer with a thickness of about 8 μm is obtained, and the surface particles are finer than those of Example 1.

[0079] (3) Annealing at 450°C for 45 min under inert atmosphere (N2), and natural (slow) cooling; annealing to improve the densification and thermal stability of the intermediate layer.

[0080] (4) Using diamond powder with an average particle size of 0.5 μm (particle size range 0.3-1.5 μm, hereinafter referred to as coarse particle size) to prepare a suspension with a mass percentage of 1%, and using diamond powder with an average particle size of 50 nm (particle size range 20-100 nm, hereinafter referred to as fine particle size) to prepare a suspension with a mass percentage of 0.8%, to conduct double-particle-size polishing (coarse first, then fine, first use the suspension containing coarse particle size diamond powder to polish for 10 min, then rinse with deionized water, ultrasonic for 3 min, and dry, then use the suspension containing fine particle size diamond powder to polish for 6 min) on the surface of the Ni-W; through the double-particle-size diamond powder composite treatment of the multi-scale rough structure, the uniformity of nucleation and film densification are enhanced.

[0081] (5) BDD film is deposited on the surface by hot wire chemical vapor deposition. The deposition temperature of the BDD film is 700°C, the hot wire temperature is 2100°C, the working atmosphere is CH4, H2 mixed gas (volume ratio is 20:500), the mixed gas is doped with vaporized (B(OCH3)3) (carrier gas H2 flow is 0.5 sccm, volume is 0.18% of the flow rate of methane gas), the pressure is 6 Torr, and the deposition time is 8 h.

[0082] Comparative Example 1 This example provides a BDD electrode, the difference between its preparation process and that of Example 1 is that it is not subjected to polishing and annealing process.

[0083] Comparative Example 2 This example provides a BDD electrode, the difference between its preparation process and that of Example 1 is that microwave CVD is used instead of hot wire vapor deposition (HFCVD) process. The difference between its process parameters and those of Example 1 is that the microwave power is 800 W.

[0084] Comparative Example 3 This example provides a BDD electrode, the difference between its preparation process and that of Example 1 is that chemical plating Ni-W is used instead of electroplating to form a Ni-W alloy layer.

[0085] The parameters in the chemical plating process are as follows: reagent (prepare 1 L of plating solution) NiSO4·6H2O: 30 g Na2WO4·2H2O: 20 g Na3C6H5O7 (trisodium citrate): 30 g (complexing agent) NH4Cl: 15 g (buffering / conducting) Deionized water is supplemented to 1 L pH adjustment: ammonia water (25%) or dilute alkali solution Chemical plating method: 1. Immediately place the treated foam substrate into a chemical plating bath at 80°C, and slowly stir to make the solution flow uniformly on the surface of the sample; 2. Keep 80℃, pH≈8.0, deposition time 60 min; 3. After taking out, rinse with deionized water thoroughly; dry naturally or dry at 60℃ for 10-20 min.

[0086] Comparative Example 4 This example provides a BDD electrode, the difference between its preparation process and that of Example 1 is that only coarse diamond is used for grinding twice in the grinding process.

[0087] Test Example The BDD electrodes prepared in the above examples and comparative examples are subjected to electrochemical stability test. Linear sweep voltammetry (LSV) is used to test the current-voltage characteristics of the BDD electrodes in an electrochemical cell, three-electrode system: the working electrode is the prepared electrode, the counter electrode is a platinum sheet, the reference electrode is a saturated calomel electrode, the electrolyte is a saturated NaCl solution, pH is about 7, the scan rate is 50 mV / s, the test voltage range is 1.0V-2.0V, and the current fluctuation is recorded.

[0088] The test results of Example 1 and Comparative Examples 1-3 are shown in Figure 6 From the figure, it can be seen that the current density of the BDD electrode prepared by the example scheme of the present application is extremely low and the side reaction inhibition effect is obvious in the high potential range. The current density of the BDD electrode prepared by the scheme of Comparative Example 1 is higher, and a small amount of side reaction occurs in the range of 1.6-2.0V. The current density of the BDD electrode prepared by the scheme of Comparative Example 2 is moderate, and the side reaction is less, but it is still significantly higher than the example group. The current density of the BDD electrode prepared by the scheme of Comparative Example 3 is higher and the side reaction occurs more frequently. The current density of the BDD electrode prepared by the scheme of Comparative Example 4 is moderate, and the side reaction is relatively less, but it is still significantly higher than the example group.

[0089] Example 2 uses a foamed nickel substrate, replaces citrate with EDTA and replaces ammonium chloride with ammonium acetate in the electroplating solution, and uses sequential grinding. The obtained electrode film is dense and evenly covered, the oxygen evolution potential is equivalent to that of Example 1, the constant potential stability is slightly inferior (current decay is less than 8% for 2h), and the side reaction current is lower. This scheme verifies the replaceability of complexing agents and conductive salts, and is suitable for foamed nickel substrates, but the comprehensive performance is slightly lower than that of Example 1.

[0090] Example 3 uses liquid trimethoxy boron (B(OCH3)3) vapor injection for boron doping on a foamed copper-nickel substrate, and uses sequential grinding process. The obtained film has fine and dense crystal grains, high quality, equivalent oxygen evolution potential to Example 1, close stability to Example 1 (current decay is less than 7% for 2h), and lower side reaction current, indicating that liquid boron source can also stably obtain high-quality BDD film.

[0091] Example 4 uses high-concentration Ni2+ / WO4 2- The electroplating solution (NiSO4·6H2O 420g / L, Na2WO4·2H2O 110g / L) forms a dense Ni-W transition layer with a thickness of about 8μm. The BDD film has high coverage and stability (the oxygen evolution potential is comparable to that of Example 1, the current decay is less than 5% after 2h, and the side reaction current is extremely low).

[0092] The experimental results above demonstrate that the diamond film electrode prepared using the method of this invention exhibits excellent electrochemical stability, especially showing stronger side reaction suppression ability under high potential conditions. Further comparative analysis of the electrode performance of the examples and comparative examples reveals a significant synergistic effect among the alloy layer formation process, surface treatment process, and deposition process—this synergistic effect not only significantly improves the adhesion and nucleation density of the BDD film but also enhances its electrochemical stability, ultimately jointly determining the overall electrochemical performance of the electrode.

[0093] The embodiments of the present invention have been described in detail above, but 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 of producing a BDD electrode, characterized by: The method comprises the following steps: S1, electroplating: taking a foamed metal material as a cathode, and forming a Ni-W alloy layer on the surface of the cathode by electroplating; S2, heat treatment: annealing the cathode after step S1 in an inert atmosphere at 400-500℃; S3, surface treatment: after the cathode after step S2 is cooled, the Ni-W alloy layer is mechanically treated with a first abrasive and a second abrasive in sequence; wherein the first abrasive and the second abrasive both contain diamond, and the average particle size of the diamond in the first abrasive is greater than that in the second abrasive; S4, deposition: depositing a boron-doped diamond layer on the surface of the cathode after step S3 by hot filament chemical vapor deposition.

2. The method of making a BDD electrode according to claim 1, wherein: The electroplating conditions in step S1 include at least one of the following conditions: 1) The plating solution contains Ni 2+ salts, tungstate salts, complexing agents and NH4CI; 2) the pH of the electroplating solution is 7-9; 3) the temperature is 50-70℃; 4) current density 1-5 A / dm 2 ; 5) the time is 10-30min.

3. The method of making a BDD electrode according to claim 2, wherein: The electroplating solution comprises the following components: NiSO4·6H2O: 180-420g / L; Na2WO4·2H2O: 45-110g / L; Na3C6H5O7: 35-85g / L; NH4Cl: 25-55g / L.

4. The method of making a BDD electrode according to claim 1, wherein: The thickness of the Ni-W alloy layer formed in step S1 is 1-10μm.

5. The method of making a BDD electrode according to claim 1, wherein: The annealing treatment time in step S2 is 30-60min.

6. The method of making a BDD electrode according to claim 1, wherein: The average particle size of the diamond in the first abrasive is 0.1-2μm; and / or, the average particle size of the diamond in the second abrasive is 50-100nm.

7. The method of making a BDD electrode according to claim 1, wherein: The deposition conditions include: hot filament temperature: 2100-2300℃, substrate temperature: 650-750℃, atmosphere: a mixed atmosphere containing CH4 and H2, and adding a boron source as a doping source.

8. The method of making a BDD electrode according to claim 7, wherein: The deposition conditions further include: pressure: 3-10Torr, deposition time: 5-10 hours.

9. A BDD electrode prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the BDD electrode according to claim 9 in the fields of sewage treatment, electrochemical sensors, electrolysis or electrocatalysis.

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