Preparation method of doped diamond-ruthenium oxide composite coating electrode and application thereof

Abstract

The application discloses a kind of doped diamond-ruthenium oxide composite coating electrode preparation method and its application, including substrate and electrode working layer being arranged on the surface of substrate, the electrode working layer is double-layer film structure, from below to above, in order to doped diamond film layer and ruthenium oxide film layer, doped diamond particles are added in the ruthenium oxide film layer.This kind of composite coating electrode combines the advantages of oxide coating electrode and doped diamond electrode, while having heterojunction effect, with good conductivity, corrosion resistance and mechanical strength, can be used for electrocatalytic wastewater degradation, chemical battery positive light weight grid, electrochemical synthesis, electric signal detection, tail gas treatment and other related electrochemical fields.

Description

TECHNICAL FIELD

[0001] The application discloses a preparation method of a doped diamond-ruthenium oxide composite coating electrode and application thereof and belongs to the technical field of electrode preparation. BACKGROUND

[0002] Doped diamond has an extremely wide electrochemical window, an extremely high oxygen evolution potential, an extremely low background current, excellent chemical stability, surface inertness and weak adsorption, and is a research hotspot in the field of environmental electrochemistry. In the field of ecological environment, the doped diamond is often used for treating difficult-to-biodegrade organic wastewater with high concentration, high salinity, high ammonia nitrogen and strong acid and alkalinity, and is called an "ideal anode material".

[0003] Electrocatalytic oxidation is called an "environment-friendly" technology, can effectively treat wastewater containing organic pollutants at normal temperature and pressure by using electrons as catalysts. With the industrialization of electrocatalytic oxidation, it is possible to apply electrocatalytic oxidation technology to large-scale field application. The selection of an anode material is the most critical in electrocatalytic oxidation. Ruthenium dioxide has good electrocatalytic oxidation characteristics and has a good oxidation degradation effect on organic wastewater.

[0004] However, although the doped diamond electrode has an extremely high oxygen evolution potential, the conductivity thereof is poor compared with a metal or an oxide film, and there are problems of low efficiency and high energy consumption in the use process; the metal oxide coating has excellent conductivity, but has a low oxygen evolution potential and poor degradation ability for refractory organic wastewater. Coupling of the doped diamond and the oxide coating can greatly improve the degradation and conductivity of the electrode. SUMMARY

[0005] In view of the defects of the prior art, a first object of the application is to provide a doped diamond-ruthenium oxide composite coating electrode which has uniform film layer coverage, excellent conductivity and electrocatalytic degradation performance.

[0006] A second object of the application is to provide a preparation method of the doped diamond-ruthenium oxide composite coating electrode.

[0007] A third object of the application is to provide an application of the doped diamond-ruthenium oxide composite coating electrode.

[0008] In order to achieve the above objects, the application adopts the following technical scheme.

[0009] The doped diamond-ruthenium oxide composite coating electrode comprises a substrate and an electrode working layer arranged on the surface of the substrate, the electrode working layer is a double-layer film structure, and from bottom to top, the doped diamond film layer and the ruthenium oxide film layer are sequentially arranged, and doped diamond particles are added to the ruthenium oxide film layer.

[0010] The inventors accidentally found that the doped diamond electrode has very high oxygen evolution potential, but compared with metal or oxide thin film, its conductivity is poor, and in use, it has low efficiency and high energy consumption. The surface of the doped diamond electrode is provided with a ruthenium oxide film layer, the ruthenium oxide film layer has excellent conductivity, and can form a PN junction with the doped diamond film layer to strengthen the separation of electrons in a constant electric field, thereby improving the current efficiency, so as to obtain a coupling electrode with excellent catalytic performance.

[0011] The doped diamond particles are introduced into the ruthenium oxide film layer, which can improve the problem of mismatching of the thermal expansion coefficients between the double-layer film, and on the other hand, the doped diamond particles are easy to form O-C bonds with the doped diamond film layer, so that through the above two aspects, the double-layer film not only has excellent bonding performance, but also further improves the conductivity.

[0012] Preferably, the substrate is selected from one of the metals nickel, niobium, tantalum, zirconium, copper, titanium, cobalt, tungsten, molybdenum, chromium, iron, or one of their alloys; or the substrate is selected from one of the ceramics Al2O3, ZrO2, SiC, Si3N4, BN, B4C, AlN, TiB2, TiN, WC, Cr7C3, Ti2GeC, Ti2AlC and Ti2AlN, Ti3SiC2, Ti3GeC2, Ti3AlC2, Ti4AlC3, BaPO3, or a doped ceramic thereof; or the substrate is selected from one of the composite materials composed of the above-mentioned metals and ceramics, or the substrate is selected from diamond or Si; preferably, the substrate is a ceramic.

[0013] The shape of the substrate is selected from at least one of powder, granular, cylindrical, cylindrical, flat plate;

[0014] The structure of the substrate is selected from at least one of a three-dimensional continuous network structure, a two-dimensional continuous network structure, and a two-dimensional closed flat plate structure.

[0015] Preferably, the thickness of the doped diamond film layer is 5-20 μm; the thickness of the ruthenium oxide film layer is 50-500 μm, preferably 80-100 μm, and the particle size of the doped diamond particles is 0.1-20 μm, preferably 10-20 μm.

[0016] The inventors found that when the thickness of the ruthenium oxide film layer and the doped diamond film layer is controlled within the above range, it is easier to form O-C bonds and intermediates, improve the adhesion of the double film, and under the synergistic effect of the above thickness, the conductivity of the final coupling electrode is optimal.

[0017] Preferably, the volume fraction of the doped diamond particles in the ruthenium oxide film layer is 0.1%-50%, preferably 20-30%.

[0018] Preferably, in the ruthenium oxide film layer, the molar ratio of ruthenium to oxygen is 1:2-8.

[0019] Preferably, the doping element in the doped diamond film layer is selected from at least one of boron, nitrogen, phosphorus, and lithium, and is preferably boron; and the doping mode is selected from at least one of constant doping, multi-layer variable doping, and gradient doping.

[0020] Preferably, the mass fraction of the doping element in the doped diamond film layer is 2‰-10‰.

[0021] The inventors have found that the doping element can react with the metal element in the oxide coating to form an intermediate product, thereby further improving the bonding force between the double-layer film.

[0022] Preferably, the doped diamond film layer forms full coating, half coating, or selective coating on the surface of the ruthenium oxide film layer, and is preferably full coating.

[0023] Preferably, the doping element in the doped diamond particle is selected from at least one of boron, nitrogen, phosphorus, and lithium, and is preferably boron; and the doping mode is selected from at least one of constant doping, multi-layer variable doping, and gradient doping.

[0024] Preferably, the mass fraction of the doping element in the doped diamond particle is 2‰-10‰.

[0025] The present application also provides a preparation method of the doped diamond-ruthenium oxide composite coating electrode. The method comprises the following steps: first, implanting nano-diamond seed crystals on the surface of a substrate; then, preparing a doped diamond film layer by chemical vapor deposition; and finally, preparing a ruthenium oxide active film layer by electrodeposition or composite thermal decomposition to obtain a double-layer film coupled electrode.

[0026] Preferably, the substrate is first ultrasonically cleaned.

[0027] Preferably, the process of implanting nano-diamond seed crystals on the surface of the substrate comprises the following steps: vertically suspending the substrate containing the ruthenium oxide active film layer in a nano-diamond seed crystal-containing suspension liquid, ultrasonically oscillating for greater than or equal to 15 minutes, and finally cleaning with alcohol and drying to obtain the nano-diamond seed crystals, wherein the particle size of the nano-diamond seed crystals is 5-20 nm, and the mass concentration of the nano-diamond seed crystals in the suspension liquid is 1-5%.

[0028] The inventors have found that the nano-diamond seed crystals are beneficial to the uniform deposition of the doped diamond film layer. However, the particle size and mass concentration of the nano-diamond seed crystals need to be effectively controlled. If the particle size of the seed crystals is small, the particles are prone to agglomeration; if the particle size of the seed crystals is large, the bonding force of the thin film is not strong; if the mass concentration of the nano-seed crystals is too high, the nano-seed crystals are prone to agglomeration; and if the mass concentration of the nano-seed crystals is too low, it is insufficient to provide enough nucleation sites for diamond growth.

[0029] Preferably, the process for preparing the doped diamond film layer by chemical vapor deposition is as follows: placing a substrate seeded with nanodiamond seeds into a chemical deposition furnace, introducing a gas mixture with a mass flow ratio of hydrogen:methane:doping gas source = 97:(1-5):(0.1-2.5), growing at a pressure of 2-5 KPa and a temperature of 600-950℃, growing for 1-4 times, taking out the substrate after each growth, replacing it and continuing to grow, each growth lasting for 1-20 hours, and the doping gas source being selected from at least one of ammonia, phosphine and borane.

[0030] Preferably, the process for preparing the ruthenium oxide film layer by the composite thermal decomposition method is as follows: dissolving 50-150 g / L of ruthenium trichloride and 10-50 g / L of hydrated ruthenium oxide in an alcohol solvent to obtain a mixed solution, adding doped diamond particles and ruthenium dioxide powder to the mixed solution and mixing uniformly to obtain a slurry, the mass ratio of the ruthenium dioxide powder, the diamond particles and the mixed solution being 0.01-10 g:0.05-250 g:1000 g, uniformly setting the slurry on a substrate by film forming, placing the substrate in an oven at 50-80℃ for 10-30 min, placing the substrate in a resistance furnace at 450-650℃ for 10-30 min, repeating the operation for 8-20 times, and finally placing the substrate in the resistance furnace for 1-2 hours to obtain the ruthenium oxide film layer.

[0031] Further preferably, the mass ratio of the ruthenium dioxide powder, the diamond particles and the mixed solution is 5 g:100-150 g:1000 g.

[0032] The inventors have found that by adding a small amount of ruthenium dioxide powder as a sintering aid in the process for preparing the ruthenium oxide film layer by the composite thermal decomposition method, the adhesion between the diamond layer and the ruthenium oxide layer can be significantly improved, and excellent conductivity and stability can be maintained during electrolysis at a large current density for a long time, and the sintering aid is the ruthenium dioxide powder.

[0033] Further preferably, the film forming method is selected from one or more of dipping, spin coating, roll coating, spraying and brushing.

[0034] Further preferably, the alcohol solvent is selected from one of anhydrous n-butanol, anhydrous ethanol, anhydrous ethylene glycol and anhydrous glycerol.

[0035] The application of the doped diamond-ruthenium oxide composite coating electrode is in the fields of electrochemical synthesis, electrochemical wastewater purification treatment, electrochemical detection and electrochemical biosensors.

[0036] Advantages

[0037] The application provides a doped diamond-ruthenium oxide composite coating electrode, which comprises a substrate and an electrode working layer arranged on the surface of the substrate, and the electrode working layer is a double-layer film structure, from bottom to top, sequentially comprising a doped diamond film layer and a ruthenium oxide film layer, and doped diamond particles are added into the ruthenium oxide film layer.

[0038] The inventors accidentally find that the doped diamond electrode has a very high oxygen evolution potential, but compared with a metal or an oxide film, the doped diamond electrode has poor conductivity, and in the use process, the doped diamond electrode has low efficiency and high energy consumption; the ruthenium oxide film layer has excellent conductivity, and can form a PN junction with the doped diamond film layer to strengthen the separation of electrons in a constant electric field, thereby improving the current efficiency, so that the electrode with the most excellent catalytic performance is obtained. DETAILED DESCRIPTION

[0039] Embodiment 1

[0040] The silicon carbide ceramic is used as the substrate, the substrate is ultrasonically cleaned, the substrate is vertically hung and immersed into a suspension liquid containing nano-diamond seeds, ultrasonic oscillation is performed for 20 min, and finally the substrate is cleaned with alcohol and dried to obtain the substrate, the particle size of the nano-diamond seeds is 5 nm, and the mass concentration of the nano-diamond seeds in the suspension liquid is 2%.

[0041] Then, the substrate with the nano-diamond seeds is placed in a chemical vapor deposition furnace, the mass flow ratio of the gases is hydrogen:methane:doping gas source=97:2:0.5, the growth pressure is 2 Kpa, the growth temperature is 800 DEG C, the growth times are 4, the substrate is taken out after each growth, and the substrate is replaced and then continuously grown, the single growth time is 10 h, and the doping gas source is borane.

[0042] The ruthenium oxide film layer is prepared by a composite thermal decomposition method, and the specific process is as follows: 100 g / L ruthenium trichloride and 15 g / L ruthenium hydrate are dissolved in anhydrous ethanol to prepare a mixed solution, boron-doped diamond particles with a particle size of 10 μm and a boron doping concentration of 3 ‰ and ruthenium dioxide powder are added into the mixed solution as sintering aids to obtain a slurry, the mass ratio of the ruthenium dioxide powder, the diamond particles and the mixed solution is 5 g:100 g:1000 g, the slurry is uniformly prepared on the substrate by brushing, and then the substrate is placed in an oven at 80 DEG C for 20 min, and then is placed in a resistance furnace for calcination at 500 DEG C for 30 min, the operation is repeated for 20 times, and the last time is calcined in the resistance furnace for 2 h.

[0043] The ruthenium oxide-doped diamond double-inert composite electrode prepared in the above embodiment 1 has a ruthenium oxide film layer with a thickness of 95 μm and a doped diamond film layer with a thickness of 17 μm. The obtained boron-doped diamond-ruthenium oxide film layer is firm and has no peeling after scratching. The volume fraction of the doped diamond particles in the ruthenium oxide film layer is 20%.

[0044] The prepared boron-doped diamond-ruthenium oxide coupling electrode is packaged, a stainless steel electrode is used as a negative electrode, 1L of active orange X-GN simulated dye wastewater with an initial concentration of 100mg / L and an electrolyte Na2SO4 concentration of 0.1mol / L is prepared, sulfuric acid is used to adjust the Ph of the solution to 3, it is placed on a magnetic stirrer, the rotating speed is adjusted to 200r / min, the current density is kept at 100mA / cm 2 during the degradation process, and the degradation is carried out for 3h, and the color removal rate of the dye reaches 98%, and the degradation is basically complete.

[0045] Example 2

[0046] Zirconium oxide ceramic is used as a substrate, the substrate is ultrasonically cleaned, the substrate is vertically suspended and immersed in a suspension containing nano-diamond seeds, ultrasonic oscillation is carried out for 20min, and finally alcohol cleaning and drying are carried out to obtain the substrate, the particle size of the nano-diamond seeds is 8nm, and the mass concentration of the nano-diamond seeds in the suspension is 2%.

[0047] Then, the substrate with the nano-diamond seeds is placed in a chemical vapor deposition furnace: the mass flow ratio of the gases is hydrogen:methane:doping gas source=97:3:1.3, the growth pressure is 3Kpa, the growth temperature is 900℃, the growth times are 4, the substrate is taken out after each growth, and the growth is continued after the substrate is replaced, the single growth time is 12h, and the doping gas source is selected as borane.

[0048] A ruthenium oxide active film layer is prepared by a composite thermal decomposition method, and the specific process is as follows: 100g / L ruthenium trichloride and 15g / L ruthenium hydrate oxide are dissolved in anhydrous ethanol to prepare a mixed solution, 20μm boron-doped diamond particles with a boron doping concentration of 3‰ and ruthenium dioxide powder as a sintering aid are added to the mixed solution, and the mixture is uniformly mixed to obtain a slurry, the mass ratio of the ruthenium dioxide powder, the diamond particles and the slurry is 5g:150g:1000g, and 5g is added; the slurry is uniformly prepared on the substrate by brushing, and then placed in an oven at 80℃ for 20min, and then placed in a resistance furnace at 500℃ for 30min, and the operation is repeated for 20 times, and the last time is baked in the resistance furnace for 2h.

[0049] The thickness of the ruthenium oxide film layer of the doped diamond and ruthenium oxide composite coating electrode prepared in the above example 2 is 100μm, and the thickness of the doped diamond film layer is 20μm. The obtained boron-doped diamond-ruthenium oxide film layer is firm and does not fall off when scratched. The volume fraction of the doped diamond particles in the ruthenium oxide film layer is 30%.

[0050] The prepared boron-doped diamond-ruthenium oxide coupling electrode was packaged, a stainless steel electrode was used as the negative electrode, 1L of active blue 19 simulated dye wastewater with an initial concentration of 100mg / L and an electrolyte Na2SO4 concentration of 0.1mol / L was prepared, and was placed on a magnetic stirrer, the rotation speed was adjusted to 150r / min, the current density was kept at 100mA / cm 2 during the degradation process, and the degradation was carried out for 2h, and the color removal rate of the dye reached 99%, and the degradation was basically complete.

[0051] Comparative example 1

[0052] The other conditions were the same as in example 1, except that no sintering aid was added when the ruthenium oxide film layer was prepared by the reheat decomposition method, the obtained ruthenium oxide film layer had poor adhesion to the substrate, and there was obvious powder falling off, and the degradation effect was much worse than that of example 1.

[0053] Comparative example 2

[0054] The other conditions were the same as in example 1, except that no doped diamond particles were added when the ruthenium oxide active film layer was prepared, and after the film was coated by the reheat decomposition method, the obtained ruthenium oxide film layer fell off when it was scratched, the film adhesion was insufficient, the heterojunction effect was poor, and the degradation effect was much worse than that of example 1.

Claims

1. A method for preparing a diamond-ruthenium oxide composite coated electrode, characterized in that: First, nanodiamond seed crystals are planted on the substrate surface, then a doped diamond film is prepared by chemical vapor deposition, and finally a ruthenium oxide active film is prepared by composite thermal decomposition to obtain a double-layer film coupled electrode. The process for preparing ruthenium oxide film using the composite thermal decomposition method is as follows: 50-150 g / L of ruthenium trichloride and 10-50 g / L of hydrated ruthenium oxide are dissolved in an alcohol solvent to obtain a mixture. Diamond particles and ruthenium dioxide powder are added to the mixture and mixed evenly to obtain a slurry. The mass ratio of ruthenium dioxide powder, diamond particles, and the mixture is 0.01-10 g: 0.05-250 g: 1000 g. The slurry is uniformly applied to a substrate using a film-forming process. The substrate is then placed in an oven at 50-80°C for 10-30 minutes, followed by calcination in a resistance furnace at 450-650°C for 10-30 minutes. This process is repeated 8-20 times, with the final calcination in the resistance furnace lasting 1-2 hours to obtain the final film. The doped diamond-ruthenium oxide composite coated electrode includes a substrate and an electrode working layer disposed on the surface of the substrate. The electrode working layer has a double-layer film structure, consisting of a doped diamond film layer and a ruthenium oxide film layer from bottom to top. Doped diamond particles are added to the ruthenium oxide film layer.

2. The method for preparing a diamond-ruthenium oxide composite coated electrode according to claim 1, characterized in that: The process of planting nanodiamond seed crystals on the substrate surface is as follows: the substrate is vertically suspended and immersed in a suspension containing nanodiamond seed crystals, ultrasonically vibrated for ≥15 min, and finally cleaned with alcohol and dried. The nanodiamond seed crystals have a particle size of 5-20 nm and a mass concentration of 1-5% in the suspension. The process of preparing doped diamond film by chemical vapor deposition is as follows: the substrate with nanodiamond seed crystals is placed in a chemical deposition furnace, the mass flow rate ratio of the introduced gas is hydrogen:methane:doped gas source = 97:(1-5):(01.-2.5), the growth pressure is 2-5 kPa, the growth temperature is 600-950℃, the number of growth cycles is 1-4, after each growth cycle, the substrate is taken out, the front and back are replaced, and then the growth continues. The time for a single growth cycle is 1-20 h. The doped gas source is selected from at least one of ammonia, phosphine, and borane.

3. The method for preparing a diamond-ruthenium oxide composite coated electrode according to claim 1, characterized in that: The film-forming method is selected from one or more of the following: dip coating, spin coating, roller coating, spray coating, and brush coating; The alcohol solvent is selected from one of anhydrous n-butanol, anhydrous ethanol, anhydrous ethylene glycol, and anhydrous glycerol.

4. The method for preparing a diamond-ruthenium oxide composite coated electrode according to claim 1, characterized in that: The substrate is selected from one of the following metals: nickel, niobium, tantalum, zirconium, copper, titanium, cobalt, tungsten, molybdenum, chromium, and iron, or an alloy thereof; or the substrate is selected from one of the following ceramics: Al2O3, ZrO2, SiC, Si3N4, BN, B4C, AlN, TiB2, TiN, WC, Cr7C3, Ti2GeC, Ti2AlC and Ti2AlN, Ti3SiC2, Ti3GeC2, Ti3AlC2, Ti4AlC3, and BaPO3, or a doped ceramic thereof; or the substrate is selected from one of the above-mentioned metal and ceramic composite materials, or the substrate is selected from diamond or Si; The substrate shape is selected from at least one of powder, granules, cylinder, tubular, and flat. The substrate structure is selected from at least one of a three-dimensional continuous network structure, a two-dimensional continuous mesh structure, and a two-dimensional closed plate structure.

5. The diamond-ruthenium oxide composite coated electrode according to claim 1, characterized in that: The thickness of the doped diamond film is 5-20µm; the thickness of the ruthenium oxide film is 50-500µm, and the particle size of the doped diamond particles is 0.1-20µm.

6. The method for preparing a diamond-ruthenium oxide composite coated electrode according to claim 1, characterized in that: The volume fraction of the doped diamond particles in the ruthenium oxide film is 0.1%-50%. In the ruthenium oxide film, the molar ratio of ruthenium to oxygen is 1:2-8.

7. The method for preparing a diamond-ruthenium oxide composite coated electrode according to claim 1, characterized in that: The doping element in the doped diamond film is selected from at least one of boron, nitrogen, phosphorus, and lithium, and the doping method is selected from one or more combinations of constant doping, multilayer variable doping, and gradient doping. The mass fraction of the doping element in the doped diamond film is 2‰-10‰. The doped diamond film forms a fully coated, partially coated, or selectively coated type on the surface of the ruthenium oxide film. The doping element in the doped diamond particles is selected from at least one of boron, nitrogen, phosphorus, and lithium, and the doping method is selected from at least one of constant doping, multilayer variable doping, and gradient doping. The mass fraction of the doping element in the doped diamond particles is 2‰-10‰.

8. The application of a diamond-ruthenium oxide composite coated electrode prepared by the preparation method according to any one of claims 1-7, characterized in that: The doped diamond and ruthenium oxide composite coated electrode is applied to the fields of electrochemical synthesis, electrochemical wastewater purification, electrochemical detection, and electrochemical biosensors.