Porous metal oxide embedded boron-doped diamond nanostructure electrode and preparation method thereof

Abstract

The invention relates to a diamond film electrode, in particular to a porous metal oxide embedded boron-doped diamond nanostructure electrode and a preparation method thereof. The electrode comprises a substrate and a boron-doped diamond film deposited on the substrate, the surface of the boron-doped diamond film is a nano-pillar array, and porous metal oxides are distributed in gaps of the nano-pillar array. The boron-doped diamond with the nano-pillar array on the surface of the electrode and the porous metal oxide can generate function synergy, play a positive role in widening the working voltage and improving the specific capacitance, and synchronously optimize the energy density performance of the electrode; the porous metal oxide is embedded in the gaps of the boron-doped diamond nanorod array, so that active substance falling caused by external factors can be effectively avoided, the structural stability of the electrode is improved, and the service life is prolonged.

Description

Technical Field

[0001] The present invention relates to a diamond thin film electrode, in particular to a porous metal oxide-embedded boron-doped diamond nanostructured electrode and a preparation method thereof. Background Art

[0002] With the intensification of the global energy crisis and the enhancement of human environmental protection awareness, various countries actively develop and utilize green new energy to replace traditional petroleum energy, such as solar energy, wind energy, and tidal energy. In this context, supercapacitors have emerged and, with the advantages of high charge and discharge efficiency, long cycle life, high power density, wide operating temperature range, and good safety and environmental protection performance, have become ideal candidates for energy storage elements. However, limited by the electrode materials and structures, supercapacitors still face the bottleneck of low energy density, seriously hindering their practical applications. According to the calculation formula E = 1 / 2CV 2 it can be seen that the energy density is affected by both the specific capacitance and the operating voltage. Boron-doped diamond has the characteristics of a wide operating voltage, low background current, and good stability, and is considered a very promising electrode material for supercapacitors. However, the specific surface area of conventional boron-doped diamond is relatively small, and the contribution of capacitance is relatively limited. Summary of the Invention

[0003] The purpose of the present invention is to solve the problems existing in the prior art. On the one hand, by constructing a nanostructure to expand the specific surface area, and on the other hand, by introducing a porous metal oxide material to compound with boron-doped diamond to provide additional pseudocapacitance, thereby improving the specific capacitance of the overall electrode and enhancing the performance of the corresponding supercapacitor.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A porous metal oxide-embedded boron-doped diamond nanostructured electrode; comprising a substrate and a boron-doped diamond thin film deposited on the substrate; the surface of the boron-doped diamond thin film is a nano-column array, and porous metal oxides are distributed in the gaps of the nano-column array.

[0005] Preferably, the height of the nano-columns is 1 - 5 μm, and the diameter of the nano-columns is 0.5 - 1 μm.

[0006] Preferably, the target material of the porous metal oxide is selected from metal oxides of Zn, Co, or Ni, and is formed by pyrolytic conversion of a metal-organic framework.

[0007] The present invention also provides a preparation method of the porous metal oxide-embedded boron-doped diamond nanostructured electrode, comprising the following steps: (1) Using physical polishing and chemical cleaning methods to perform surface treatment on the growth substrate; (2) Using hot filament chemical vapor deposition method to deposit a layer of boron-doped diamond thin film on the surface of the growth substrate; (3) The method of ultraviolet ozone activation is adopted to improve the hydrophilicity of the boron-doped diamond surface; (4) The method of water evaporation capillary force is adopted to deposit a monolayer of TiO2 microspheres on the boron-doped diamond surface; (5) The method of oxygen plasma etching is adopted to construct a nano-column array structure on the boron-doped diamond surface with a monolayer of TiO2 microspheres as a mask; (6) The method of wet chemical etching is adopted to remove the TiO2 microspheres; (7) The method of magnetron sputtering is adopted to deposit a metal oxide film on the surface of the boron-doped diamond nano-column array; (8) The method of solvothermal is adopted to grow a metal-organic framework with the metal oxide as a sacrificial template; (9) The method of air pyrolysis is adopted to convert the metal-organic framework into a porous metal oxide with the metal-organic framework as a precursor; the pyrolysis temperature is 300 °C, and the pyrolysis time is 1-2 h.

[0008] In the above scheme, the growth substrate in step (1) is single crystal silicon, the physical polishing includes polishing with sandpaper and polishing cloth, and the chemical cleaning includes ultrasonic cleaning with acetone, absolute ethanol, and ultrapure water for 10 min each.

[0009] In the above scheme, in step (2), methane is used as the carbon source with a volume ratio of 1-5%, hydrogen is used as the auxiliary gas with a volume ratio of 95-99%, trimethylborane is used as the boron source, and the mass concentration range of boron in the mixed gas is 6000-8000 ppm. The reaction temperature is 450-650 °C, and the reaction time is 5-20 h. A boron-doped diamond film with a thickness of 5-20 μm is deposited on the substrate.

[0010] In the above scheme, in step (3), the oxygen flux is 0.5-1 cm 3 min -1 , the heating temperature is 50-100 °C, and the ultraviolet irradiation time is 5-15 min.

[0011] In the above scheme, in step (4), a 0.5-1.0 µm TiO2 microsphere suspension is adopted.

[0012] In the above scheme, in step (5), the operating oxygen pressure is 10-20 Pa, the oxygen flux is 10-20 cm 3 s -1 , the plasma power is 100-150 W, and the etching time is 30-90 min.

[0013] In the above scheme, in step (6), the TiO2 microspheres are removed with an HF-HNO3 solution; where the HF-HNO3 solution contains 24 wt% HF and 30 wt% HNO3.

[0014] In the above solution, in step (7), the target material is a metal oxide of Zn, Co, or Ni, the radio frequency power is 200 W, the working pressure is 7.5×10-3 Torr, and the sputtering time is 1 - 2 min.

[0015] In the above solution, in step (8), 0.3 g of 2-methylimidazole and 200 μL of concentrated hydrochloric acid are dissolved in 10 ml of deionized water and stirred for 30 min, and then transferred to a high-pressure reaction kettle with a 20 ml polytetrafluoroethylene liner; using a polytetrafluoroethylene support, the boron-doped diamond with a sputtered metal oxide is hung face down in the middle of the solution. The container is sealed and reacted at 80°C for 6 - 12 h.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The boron-doped diamond with a nanocolumn array on the surface and the porous metal oxide can produce functional synergy, play a positive role in broadening the working voltage and increasing the specific capacitance, and synchronously optimize the energy density performance of the electrode; (2) The porous metal oxide is embedded in the gaps of the nanocolumn array of the boron-doped diamond, which can effectively prevent the active substance from falling off caused by external factors, improve the structural stability of the electrode, and extend the working life. Description of the Drawings

[0017] Figure 1 It is a simplified process schematic diagram of the preparation method of the boron-doped diamond nanostructure electrode with porous metal oxide embedded in the embodiment of the present invention; In the figure, 1 is a single-crystalline silicon growth substrate; 2 is a boron-doped diamond thin film; 3 is a TiO2 microsphere; 4 is a boron-doped diamond thin film with a nanocolumn array on the surface; 5 is a metal oxide thin film; 6 is a metal-organic framework; 7 is a porous metal oxide; Figure 2 It is a cross-sectional SEM image of the boron-doped diamond nanostructure electrode with porous metal oxide embedded prepared in the embodiment of the present invention; Figure 3 It is a comparison diagram of CV curves of the boron-doped diamond nanostructure electrode with porous metal oxide embedded, the conventional boron-doped diamond thin film electrode, and the boron-doped diamond thin film electrode with a nanocolumn array on the surface prepared in the embodiment of the present invention in a 1 M H2SO4 solution; In the figure, Ⅰ corresponds to the conventional boron-doped diamond thin film electrode; Ⅱ corresponds to the boron-doped diamond thin film electrode with a nanocolumn array on the surface; Ⅲ corresponds to the boron-doped diamond nanostructure electrode with porous metal oxide embedded. Detailed Embodiments

[0018] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings.

[0019] The porous metal oxide-embedded boron-doped diamond nanostructured electrode provided by this embodiment has a boron-doped diamond film with a thickness of 20 μm, nanorods with a height of 5 μm and a diameter of 0.5 μm. The porous metal oxide is distributed in the gaps of the nanorod array. Among them, the target material of the porous metal oxide is selected as the metal oxide of Zn, which is formed by the pyrolytic conversion of a metal-organic framework.

[0020] The preparation method of the porous metal oxide-embedded boron-doped diamond nanostructured electrode provided by this embodiment has a process as Figure 1 shown, and the specific steps are as follows: (1) The surface of single-crystal silicon 1 is treated by physical polishing and chemical cleaning. Physical polishing includes polishing with sandpaper and polishing cloth, and chemical cleaning includes ultrasonic cleaning with acetone, absolute ethanol, and ultrapure water for 10 min each; (2) By the method of hot-filament chemical vapor deposition, using methane as the carbon source with a volume ratio of 5%, hydrogen as the auxiliary gas with a volume ratio of 95%, and trimethylborane as the boron source, the mass concentration range of boron in the mixed gas is 8000 ppm, the reaction temperature is 650 °C, and the reaction time is 20 h. A boron-doped diamond film 2 with a thickness of 20 μm is deposited on single-crystal silicon 1; (3) By the method of ultraviolet ozone activation, the hydrophilicity of the boron-doped diamond surface is improved. The oxygen flux is 0.5 cm 3 min -1 , the heating temperature is 100 °C, and the ultraviolet irradiation time is 10 min; (4) By the method of water evaporation capillary force, TiO2 microspheres 3 with a diameter of 1.0 µm are deposited on the boron-doped diamond surface; (5) By the method of oxygen plasma etching, using a monolayer of TiO2 microspheres as a mask to construct a nanorod array structure 4 on the boron-doped diamond surface. The operating oxygen pressure is 20 Pa, the oxygen flux is 20 cm3 s-1, the plasma power is 150 W, and the etching time is 60 min; (6) By the method of wet chemical etching, the TiO2 microspheres are removed with an HF-HNO3 solution (HF 24 wt %, HNO3 30 wt %); (7) By the method of magnetron sputtering, a metal oxide film 5 is deposited on the surface of the boron-doped diamond nanorod array. The target material is ZnO, the radio frequency power is 200 W, the working pressure is 7.5×10-3 Torr, and the sputtering time is 2 min; (8) Using the solvothermal method, with metal oxide as the sacrificial template, metal-organic framework 6 was grown. 0.3 g of 2-methylimidazole and 200 μL of concentrated hydrochloric acid were dissolved in 10 ml of deionized water and stirred for 30 min, then transferred to a 20 ml Teflon-lined autoclave; using a Teflon support, the boron-doped diamond sputtered with metal oxide was suspended face down in the middle of the solution; the container was sealed and reacted at 80 °C for 12 h; (9) Using the air pyrolysis method, with metal-organic framework as the precursor, porous metal oxide 7 was transformed. The pyrolysis atmosphere was air, the pyrolysis temperature was 300 °C, and the pyrolysis time was 2 h.

[0021] The cross-sectional SEM image of the porous metal oxide-embedded boron-doped diamond nanostructured electrode prepared in this example is as Figure 2 shown. It can be seen from Figure 2 that the porous metal oxide is evenly distributed in the gaps of the boron-doped diamond nanorod array.

[0022] The comparison diagram of the CV curves of the porous metal oxide-embedded boron-doped diamond nanostructured electrode prepared in this example, the conventional boron-doped diamond thin film electrode, and the boron-doped diamond thin film electrode with a nanorod array on the surface in 1 M H2SO4 solution is as Figure 3 shown. It can be seen from Figure 3 that the porous metal oxide-embedded boron-doped diamond nanostructured electrode prepared by the present invention has a significant improvement in capacitance performance compared with the conventional boron-doped diamond thin film electrode.

Claims

1. A porous metal oxide embedded boron-doped diamond nanostructure electrode; comprising a substrate and a boron-doped diamond film deposited on the substrate; the surface of the boron-doped diamond film is a nanocolumn array, characterized in that: Porous metal oxide is distributed in the gaps of the nano-column array.

2. The porous metal oxide embedded boron-doped diamond nanostructure electrode according to claim 1, characterized in that: The height of the nanocolumns is 1 to 5 μm, and the diameter of the nanocolumns is 0.5 to 1 μm.

3. The porous metal oxide embedded boron-doped diamond nanostructure electrode according to claim 1, characterized in that: The target material of the porous metal oxide is selected from metal oxides of Zn, Co or Ni, and is formed by thermal decomposition and conversion of a metal organic framework.

4. The method for preparing the porous metal oxide embedded boron-doped diamond nanostructure electrode according to any one of claims 1 to 3, characterized in that: The steps include: (1) Physical polishing and chemical cleaning are used to treat the surface of the growth substrate; (2) Depositing a boron-doped diamond film on the surface of the growth substrate using a hot wire chemical vapor deposition method; (3) Using UV-ozone activation method to improve the hydrophilicity of the boron-doped diamond surface; (4) Using the capillary force of water evaporation, a single layer of TiO2 microspheres is deposited on the surface of boron-doped diamond; (5) Using oxygen plasma etching, a nanorod array structure was constructed on the surface of boron-doped diamond using a single layer of TiO2 microspheres as a mask; (6) Using wet chemical etching method to remove TiO2 microspheres; (7) Depositing a metal oxide film on the surface of the boron-doped diamond nanorod array by magnetron sputtering; (8) Using a solvothermal method, metal oxides were used as sacrificial templates to grow metal organic frameworks; (9) The porous metal oxides were converted by air pyrolysis with metal organic frameworks as precursors; the pyrolysis temperature was 300 °C and the pyrolysis time was 1 to 2 h.

5. The preparation method according to claim 4, characterized in that: In step (2), methane is used as the carbon source in a volume ratio of 1 to 5%, hydrogen is used as the auxiliary gas in a volume ratio of 95 to 99%, trimethylborane is used as the boron source, the mass concentration of boron in the mixed gas ranges from 6000 to 8000 ppm, the reaction temperature is 450 to 650° C., the reaction time is 5 to 20 hours, and a boron-doped diamond film with a thickness of 5 to 20 μm is deposited on the substrate.

6. The preparation method according to claim 4, characterized in that: The oxygen flux in step (3) is 0.5 to 1 cm 3 min -1 , the heating temperature is 50-100°C, and the ultraviolet irradiation time is 5-15 min.

7. The preparation method according to claim 4, characterized in that: In step (4), a 0.5-1.0 µm TiO2 microsphere suspension is used.

8. The preparation method according to claim 4, characterized in that: In step (5), the operating oxygen pressure is 10-20 Pa and the oxygen flux is 10-20 cm 3 s -1 , plasma power is 100-150 W, and etching time is 30-90 min.

9. The preparation method according to claim 4, characterized in that: In step (6), the TiO2 microspheres are removed using a HF-HNO3 solution; wherein the HF-HNO3 solution contains 24 wt % HF and 30 wt % HNO3.

10. The preparation method according to claim 4, characterized in that: In step (7), the target material is metal oxides of Zn, Co, and Ni, the RF power is 200 W, the working pressure is 7.5×10-3 Torr, and the sputtering time is 1 to 2 min.

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