Method for preparing ZnO@BDD thin film by electrodeposition

Abstract

This invention provides a method for preparing ZnO@BDD thin films by electrodeposition, belonging to the field of diamond thin film technology. This invention uses electrochemical deposition to prepare zinc oxide thin films on boron-doped diamond substrates, forming a ZnO@BDD composite structure. In preparing the zinc oxide and boron-doped diamond composite thin film, the adjustment of the deposition voltage is crucial, playing a significant role in the formation of micron-scale conical structures and orientation distribution. Under constant potential deposition conditions of -0.7V to -1.1V, the resulting structural orientation distribution provides more active sites, and tests show that it exhibits better electrochemical performance. The resulting symmetrical supercapacitor has good stability and reusability, and the preparation method is simple and suitable for large-scale fabrication.

Description

Technical Field

[0001] This invention belongs to the field of diamond thin film technology, specifically relating to a method for preparing micron-scale diamond films and their application as electrochemical electrodes. Background Technology

[0002] Boron-doped diamond (BDD) possesses high conductivity, excellent corrosion resistance, and a unique advantage of a wide operating potential window in both aqueous and non-aqueous electrolytes. This could enable supercapacitors to achieve high energy and power densities, allowing for the fabrication of high-performance electrochemical electrodes. Zinc oxide (ZnO) is readily grown on various substrates at relatively low temperatures. Zinc oxide and boron-doped diamond heterostructures (ZnO@BDD) have been reported to be prepared via hydrothermal, sol-gel, and thermal evaporation methods. However, current preparation methods all have certain drawbacks. For example, the hydrothermal method requires long processing times and high growth costs; the sol-gel method suffers from discontinuous processing and long processing times, making it unsuitable for mass production; and the thermal evaporation method requires a strict vacuum level in the deposition chamber to grow high-quality zinc oxide films, which limits its further development. Summary of the Invention

[0003] To address the above problems, this invention proposes a method for preparing ZnO@BDD thin films by electrodeposition. The technical solution adopted in this invention is as follows:

[0004] The specific steps for preparing ZnO@BDD thin films by electrodeposition are as follows:

[0005] 1) Preparation of boron-doped diamond (BDD) thin films using chemical vapor deposition (CVD):

[0006] A cleaned silicon wafer was used as a growth substrate, and a polycrystalline boron-doped diamond film was deposited on the substrate by chemical vapor deposition. During the vapor deposition process, a mixture of hydrogen (H2) and methane (CH4) with a CH4 / H2 volume ratio of 5% was used as the reaction source, and the boron source was trimethyl borate (C3H9BO3) introduced by hydrogen. The pressure in the reaction chamber was 12 kPa, and the substrate temperature was 900℃.

[0007] 2) Electrodeposition to form ZnO@BDD thin films:

[0008] A standard three-electrode system was used. The electrolyte was a mixed solution prepared by 0.02 mol / L zinc nitrate solution, 0.01 mol / L hexamethylenetetramine solution and 0.01 mol / L ammonium acetate solution in a volume ratio of 1:1:1. The BDD film obtained in step 1) was used as the working electrode, Ag / AgCl (3M KCl) was used as the reference electrode and Pt was used as the counter electrode. Electrodeposition was performed at 90°C with a constant potential control of -0.7V to -1.1V to deposit a ZnO film on the boron-doped diamond film to obtain a ZnO@BDD film.

[0009] Preferably, the silicon wafer cleaned in step 1) is ground on sandpaper containing diamond powder for 15 minutes, then ultrasonically treated in alcohol containing diamond powder with a particle size of 5-10nm for 1 hour, and finally ultrasonically cleaned in sequence with acetone, alcohol and deionized water.

[0010] The chemical vapor deposition methods include microwave plasma chemical vapor deposition (MPCVD), hot filament chemical vapor deposition (HFCVD), and hot cathode direct current plasma chemical vapor deposition (DCCVD).

[0011] The thin film prepared by this invention can be used as an electrode for symmetrical supercapacitors.

[0012] The beneficial effects of this invention are:

[0013] 1. The preparation method provided by the present invention has the advantages of fast deposition rate, wide applicability and large deposition area. More importantly, the microstructure morphology can be controlled by selecting conditions. The process is simple and easy to prepare on a large scale.

[0014] 2. The ZnO@BDD thin film prepared by this invention has the characteristics of uniform orientation and distribution.

[0015] 3. The ZnO@BDD thin film prepared by this invention can be used as an electrochemical electrode. Its surface structure greatly increases the surface area of ​​the electrode, resulting in excellent electrochemical performance. The ZnO@BDD electrode exhibits excellent electrochemical performance at a current density of 5 μA·cm⁻¹. -2 At that time, the electrode capacitance reached 2200 μF·cm. -2 The capacitance retention rate reached 94.181% after 20,000 cycles, exceeding that of the BDD electrode. A symmetrical supercapacitor fabricated using two ZnO@BDD electrodes achieved a capacitance retention rate of 0.34 kW·kg⁻¹. -1 A power density of 0.16 Wh·kg was achieved. -1 Energy density at 20 μA·cm -2 825 μF·cm was obtained at the scan rate. -2 The capacitance at 1 mA·cm -2After 25,000 charge-discharge cycles at the specified current density, the capacitance decreased by only 6.868%. Attached Figure Description

[0016] Figure 1 (a) is a scanning electron microscope image of BDD grown on a silicon substrate; (b) is a SEM image of a ZnO@BDD thin film prepared at -0.9V; (c) is a SEM image of a ZnO@BDD thin film prepared at -1.0V; the inset is an image obtained under a high magnification microscope; and (d) is a SEM image of a ZnO@BDD thin film prepared at -1.1V.

[0017] Figure 2 (a)-(e) SEM images and corresponding EDS mappings of B, C, O and Zn elements in the BDD@ZnO electrode, and (f) and (g) are low-magnification and high-magnification TEM images of the ZnO microrod, respectively.

[0018] Figure 3 Electrochemical characterization of BDD@ZnO: (a) Scan rates in the range of 10–200 mV·s -1 CV curves within the range, (b) 5~20μA·cm -2 GCD curves recorded at current densities, (c) 5–50 μA·cm -2 GCD curve at current density, (d) 1 mA·cm -2 Cyclic stability at current density.

[0019] Figure 4 Electrochemical performance of a symmetrical supercapacitor assembled with two BDD@ZnO electrodes: (a) 100 mV·s at different potential windows -1 The CV curves recorded below, (b) scan rate range of 10-50 mV·s within the 0-1.6V potential window. -1 The CV curves are shown below, (c) with current densities of 20-100 μA·cm. -2 The GCD curves obtained below (d) show current densities of 15-100 mA·g. -1 The GCD curves obtained below, (e) have a frequency range of 10. 5 ~10 -2 The impedance spectrum of Hz, (f) supercapacitor device at a current density of 1 mA·cm -2 Cyclic stability at that time. Detailed Implementation

[0020] The present application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present application and are not intended to limit it in any way.

[0021] Example 1: Preparation of boron-doped diamond thin films on silicon wafer substrates

[0022] A 1cm × 1cm silicon wafer was selected as the growth substrate. First, the wafer was cleaned to remove surface contaminants. To improve the nucleation density during growth, the growth surface was ground on sandpaper containing diamond powder for 15 minutes, then ultrasonically treated in alcohol containing diamond powder for 1 hour. Finally, it was ultrasonically cleaned sequentially with acetone, alcohol, and deionized water, dried, and placed in a CVD reaction chamber to deposit a diamond film. During vapor deposition, a mixture of hydrogen (H2) and methane (CH4) with a CH4 / H2 ratio of 5% was used as the reaction source, and the boron source was trimethyl borate (C3H9BO3) introduced by hydrogen. During deposition, the pressure inside the reaction chamber was 12 kPa, and the substrate temperature was approximately 900℃. After 12 hours of deposition, the thickness of the BDD film was approximately 20 μm.

[0023] Example 2: Preparation of zinc oxide diamond composite structure

[0024] A standard three-electrode system was used, with the electrolyte being a mixed solution prepared from 0.02 mol / L zinc nitrate solution, 0.01 mol / L hexamethylenetetramine solution, and 0.01 mol / L ammonium acetate solution in a volume ratio of 1:1:1. The BDD film obtained in Example 1 was used as the working electrode, Ag / AgCl (3M KCl) as the reference electrode, and Pt as the counter electrode. Electrodeposition was performed at 90°C using a constant potential control method.

[0025] Potentials of -0.9V, -1.0V, and -1.1V were applied to find a suitable potential. The extracted samples were deposited and grown, then dried in air to obtain the prepared samples. The mass loadings of the ZnO@BDD electrode were approximately 11, 15, and 21 mg cm⁻¹ at voltages of -0.9V, -1.0V, and -1.1V, respectively. -2 . Figure 1 The surface morphology of the films under different voltages was shown, exhibiting a micron-scale conical structure. The deposition voltage plays a significant role in the formation of these micron-sized cones and their orientation distribution. By modulating the film morphology with voltage, the sample treated at a deposition voltage of -1.0 V showed relatively uniform ZnO growth, resulting in a larger specific surface area, which may enhance electrochemical activity.

[0026] Example 3: Electrochemical testing as an electrode

[0027] Current-voltage characteristic curves and charge-discharge curves of ZnO@BDD electrode at different scan rates and current densities. Figure 3 It maintains a stable shape at continuously increasing scan rates, exhibiting stable ideal capacitance characteristics. This is true at current densities of 5–20 μA·cm⁻¹. -2At this time, the GCDs exhibit an almost symmetrical linear shape, indicating that the electrode possesses high reversibility and high coulombic efficiency. The maximum specific capacitance is 2.259 F·g. -1 As the number of cycles increased, the capacitance remained high. After 20,000 cycles, the capacitance remained at 94.181% of its initial value, indicating that the electrochemical stability of the ZnO@BDD electrode was satisfactory.

[0028] Example 4: Electrochemical Testing of Assembled Symmetrical Supercapacitor

[0029] Figure 4 The results show the electrochemical test findings after assembling the device using two ZnO@BDD electrodes as the negative and positive electrodes, and 1M Na2SO4 as the electrolyte. Figure 4 As shown in (a), when the potential window is increased to 1.8V, the CV curve still remains rectangular, indicating excellent reversibility. Figure 4 (b) shows a scan rate of 10–50 mV·s. -1 The CV curve, showing no significant distortion, demonstrates ideal capacitive behavior within the 0–1.6V potential window. This is achieved at current densities ranging from 20 to 100 mA·cm⁻¹. -2 The constant triangle of the GCD curve recorded at the specified time indicates high reversibility. This is true when the current density is 20 μA·cm⁻¹. -2 At that time, the area specific capacitance was at its maximum (825 μF·cm). -2 The corresponding specific capacitance value is 0.45 F·g. -1 The series resistance Rs and charge transfer resistance Rct of the device are both 2.944 Ω·cm. -1 and 1.777Ω·cm -1 A smaller Rct indicates a smoother ion transport process. After 25,000 cycles, the capacitance remained at 93.132% of its initial value, demonstrating good electrochemical stability.

Claims

1. A method for preparing ZnO@BDD thin films by electrodeposition, characterized in that, The specific steps of this method are as follows: 1) Preparation of boron-doped diamond thin films using chemical vapor deposition: A cleaned silicon wafer was used as a growth substrate, and a polycrystalline boron-doped diamond film was deposited on the substrate by chemical vapor deposition. During the vapor deposition process, a mixture of hydrogen and methane with a CH4 / H2 volume ratio of 5% was used as the reaction source, and the boron source was trimethyl borate introduced by hydrogen. The pressure in the reaction chamber was 12 kPa, and the substrate temperature was 900℃. 2) Electrodeposition to form ZnO@BDD thin films: A standard three-electrode system was used. The electrolyte was a mixed solution prepared by 0.02 mol / L zinc nitrate solution, 0.01 mol / L hexamethylenetetramine solution and 0.01 mol / L ammonium acetate solution in a volume ratio of 1:1:

1. The boron-doped diamond film obtained in step 1) was used as the working electrode, Ag / AgCl (3M KCl) was used as the reference electrode and Pt was used as the counter electrode. Electrodeposition was performed at 90°C with a constant potential control of -0.7V to -1.1V to obtain a ZnO@BDD film.

2. The method for preparing ZnO@BDD thin films by electrodeposition according to claim 1, characterized in that, The silicon wafers cleaned in step 1) are ground on sandpaper containing diamond powder for 15 minutes, and then ultrasonically treated in alcohol containing diamond powder with a particle size of 5-10nm for 1 hour. Finally, they are ultrasonically cleaned in sequence with acetone, alcohol and deionized water.

3. The method for preparing ZnO@BDD thin films by electrodeposition according to claim 1, characterized in that, The potential is -1.0V.

4. The method for preparing ZnO@BDD thin films by electrodeposition according to claim 1, characterized in that, The chemical vapor deposition methods include: microwave plasma chemical vapor deposition, hot filament chemical vapor deposition, and hot cathode direct current plasma chemical vapor deposition.

5. A ZnO@BDD thin film prepared by the method according to any one of claims 1 to 4.

6. Use of the ZnO@BDD thin film according to claim 5 as an electrode for a symmetrical supercapacitor.

Images