Nano-diamond / graphene composite film electrode with high hydrogen evolution potential and high electrochemical activity and preparation method thereof

Abstract

The present invention discloses a nano-diamond / graphene composite thin film electrode having both high hydrogen evolution potential and high electrochemical activity and a preparation method thereof. The method increases the number of electrochemical reaction active sites of the composite thin film electrode and improves its hydrogen evolution potential, and finally obtains a nano-diamond / graphene composite thin film electrode having both high hydrogen evolution potential and high electrochemical activity, which has great application prospects in the fields of electrochemical electrode materials and electrochemical energy storage.

Description

Technical Field

[0001] The invention relates to the field of diamond cathode materials, and in particular to a nano-diamond / graphene composite film electrode having both high hydrogen evolution potential and high electrochemical activity and a preparation method thereof. Background Art

[0002] In industrial applications, cathode materials play a pivotal role. The cathode hydrogen evolution reaction is regarded as one of the most challenging competitive reactions among most key cathode reactions, which greatly reduces the reaction efficiency of the target reaction. Diamond electrodes have excellent physical and chemical properties, such as high hardness, strong corrosion resistance, strong resistance to surface contamination and long service life. In addition, diamond electrodes have an extremely wide potential window (>3.5 V), that is, high hydrogen and oxygen evolution overpotentials, which makes them widely concerned in the field of electrochemistry and are a cathode material with great potential.

[0003] Common diamond thin film electrodes are mainly boron-doped diamond (BDD), and their hydrogen evolution potential is only ~-1.5 V. Although this electrode has excellent electrochemical reaction activity, it still cannot meet the needs of being a high-performance cathode material. By changing the termination group type on the surface of the BDD electrode to functional groups such as O and F through plasma treatment, its hydrogen evolution potential can be negatively shifted to ~-1.8 V (vs RHE); introducing a small amount of graphene into the low B-doped BDD electrode can also negatively shift the hydrogen evolution potential to ~-2.0V (vs RHE). However, the electrochemical reaction activity of the diamond electrodes obtained by the above methods is extremely low and cannot be used as an effective cathode material. Therefore, there is currently no diamond cathode material that has both high hydrogen evolution potential [>-1.5 V (vs RHE)] and high electrochemical activity.

[0004] In the authorized patents of this research group, the hot wire pressure for growing diamond films is usually controlled at 1.3-2.2kPa; in the published patent CN202310203918, a two-step method was used to prepare vertical nanodiamond / graphene composite sheet thin film electrodes by hot wire chemical vapor deposition. In the first step, the growth pressure was controlled to 1.6 kPa, the growth time to 20 min, the growth power to 2200 W, the high-purity hydrogen flow rate to 200 sccm, and the acetone / high-purity hydrogen flow rate to 90 sccm. A thin layer composed of single nanodiamond particles was first deposited on a silicon substrate; in the second step, the carbon source was turned off, and the growth pressure was adjusted to 1.6 kPa, the growth power to 1800 W, the growth time to 3 min, and the high-purity hydrogen flow rate to 100 sccm to grow vertical nanodiamond / graphene composite sheets on the nanodiamond particles, thereby preparing vertical nanodiamond / graphene composite sheet thin film electrodes. The bottom of the electrode is composed of single nano-diamond particles, with the silicon substrate exposed, which affects its electrochemical performance.

[0005] The present invention adopts the hot wire chemical vapor deposition method to prepare the nano-diamond / graphene composite thin film electrode, reduces the growth gas pressure to 1.0 kPa, prolongs the growth time to 90 min, prepares the continuous and dense nano-diamond / graphite composite thin film with smaller diamond and graphene grain sizes and without exposed silicon substrate, and then performs thermal oxidation treatment on the film in the air, utilizes the etching effect of oxygen on the graphite phase in the film to increase its edge defects, that is, to increase the number of active sites of its electrochemical reaction, so that the electrochemical active area of ​​the nano-diamond / graphene composite thin film electrode after thermal oxidation treatment can reach 5324.1 μC / cm 2 , the highest hydrogen evolution potential can reach -1.98 V (vs RHE). Compared with traditional cathode electrodes, such as Pd electrode with high hydrogen evolution potential ~-0.6 V (vs RHE), glassy carbon electrode ~-1.2 V (vs RHE), and BDD electrode ~-1.5 V (vsRHE), this electrode has a higher hydrogen evolution potential and a larger electrochemical active area, that is, a higher electrochemical reaction activity, and can be used as a high overpotential cathode material. Summary of the invention

[0006] The present invention aims to provide a nano-diamond / graphene composite thin film electrode having both high hydrogen evolution potential and high electrochemical activity and a preparation method thereof. The present invention first prepares a continuous and dense nano-diamond / graphene composite thin film electrode by hot wire chemical vapor deposition, and then performs thermal oxidation treatment on the composite thin film electrode to increase the number of electrochemical reaction active sites of the composite thin film electrode and improve its hydrogen evolution potential, and finally obtains a nano-diamond / graphene composite thin film electrode having both high hydrogen evolution potential and high electrochemical activity. The present invention is of great significance for expanding the application of diamond thin film electrodes in the field of electrochemistry.

[0007] The technical solution of the present invention is as follows:

[0008] A nano-diamond / graphene composite film electrode having both high hydrogen evolution potential and high electrochemical activity is prepared by the following method:

[0009] (1) Pre-treating a single crystal silicon wafer with a diamond seeding liquid to obtain a seeded single crystal silicon wafer;

[0010] The preparation method of diamond seed solution is as follows: diamond powder (particle size 500 nm) is mixed with deionized water, and ultrasonically dispersed uniformly to obtain; preferably, the mass volume ratio of diamond powder to deionized water is 1:100, g / mL;

[0011] The seeding operation is as follows: take diamond seeding liquid on the polishing flannel, grind the single crystal silicon wafer back and forth at the seeding liquid to grind the seeding crystal, and the grinding time is 20 minutes; then place the single crystal silicon wafer after the seeding crystal is ground in the diamond seeding liquid, and ultrasonic seeding is performed for 30 minutes; then take out the single crystal silicon wafer, wash it with deionized water, and blow it dry with nitrogen to obtain the single crystal silicon wafer after seeding;

[0012] (2) using the seeded single crystal silicon wafer obtained in step (1) as a substrate, and preparing a continuous and dense nanodiamond / graphene composite thin film electrode by hot wire chemical vapor deposition;

[0013] The specific operation is as follows: a single crystal silicon wafer after seeding is placed in a hot wire chemical vapor deposition device, a tantalum wire is used as a metal wire, acetone is used as a carbon source, acetone is brought into the reaction chamber by bubbling high-purity hydrogen with a flow rate of 80 sccm, and high-purity hydrogen with a flow rate of 200 sccm is also introduced, the growth power is controlled to be 2200 W, the growth pressure is 1.0 kPa, and the growth time is 90 min. After the growth is completed, the acetone is stopped, and the voltage is reduced to 0 V at a rate of 1 V / min in a high-purity hydrogen atmosphere, so that the power is reduced to 0 W, and a nanodiamond / graphene composite thin film electrode is obtained;

[0014] (3) placing the nanodiamond / graphene composite thin film electrode prepared in step (2) in a muffle furnace for thermal oxidation treatment to obtain the nanodiamond / graphene composite thin film electrode having both high hydrogen evolution potential and high electrochemical activity;

[0015] Set the muffle furnace temperature to 500-700 °C (preferably 600 °C) and the thermal oxidation treatment time to 10-50 min (preferably 30-40 min).

[0016] The beneficial effects of the present invention are mainly reflected in:

[0017] 1. The composite thin film electrode is treated with a muffle furnace, which can effectively regulate the graphene and diamond microstructures on the film surface. It is easy to operate and can obtain electrode materials with excellent electrochemical reaction activity without doping;

[0018] 2. The film electrode has extremely high hydrogen evolution potential and great electrochemical reaction activity. Its hydrogen evolution potential can reach up to ~-1.98 V (vs RHE), which is higher than that of traditional metal lead electrode [~-0.8 V (vs RHE)], and the electrochemical active area reaches 5324μC / cm 2 , higher than conventional graphite electrodes (~2000 μC / cm 2 ), which has great application prospects in the field of electrochemical electrode materials and electrochemical energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 : FESEM image of the nanodiamond / graphene composite thin film electrode NCD-G-10 thermally oxidized at 600°C for 10 min in Example 1.

[0020] Figure 2 : The nanodiamond / graphene composite film electrode NCD-G-10 thermally oxidized at 600 °C for 10 min in Example 1 has a wave number of (a) 800-2200 cm -1 and (b) 2200-3500 cm -1 Raman spectrum of .

[0021] Figure 3 : The nanodiamond / graphene composite film electrode NCD-G-10 thermally oxidized at 600 °C for 10 min in Example 1 is (a) 0.5 MH 2 SO 4 and (b) 1 M KCl + 1 mM K 3 Fe(CN) 6 CV curves in electrolyte at a scan rate of 100 mV / s.

[0022] Figure 4 : The nanodiamond / graphene composite film electrode NCD-G-10 thermally oxidized at 600°C for 10 min in Example 1 was heated to 0.5 MH 2 SO 4 (a) Polarization curve and (b) Tafel slope plot of LSV test at a scan rate of 100 mV / s in electrolyte.

[0023] Figure 5 : FESEM image of the nanodiamond / graphene composite thin film electrode NCD-G-30 thermally oxidized at 600°C for 30 min in Example 2.

[0024] Figure 6 : HRTEM image of the nanodiamond / graphene composite thin film electrode NCD-G-30 thermally oxidized at 600°C for 30 min in Example 2.

[0025] Figure 7 : The nanodiamond / graphene composite film electrode NCD-G-30 thermally oxidized at 600 °C for 30 min in Example 2 has a wave number of (a) 800-2200 cm -1 and (b) 2200-3500 cm -1 Raman spectrum of .

[0026] Figure 8: The nanodiamond / graphene composite film electrode NCD-G-30 thermally oxidized at 600 °C for 30 min in Example 2 is (a) 0.5 MH 2 SO 4 and (b) 1 M KCl + 1 mM K 3 Fe(CN) 6 CV curves in electrolyte at a scan rate of 100 mV / s.

[0027] Fig. 9 : The nanodiamond / graphene composite film electrode NCD-G-30 thermally oxidized at 600°C for 30 min in Example 2 was heated to 0.5 MH 2 SO 4 (a) Polarization curve and (b) Tafel slope plot of LSV test at a scan rate of 100 mV / s in electrolyte.

[0028] Fig.10 : FESEM image of the nanodiamond / graphene composite thin film electrode NCD-G-50 thermally oxidized at 600°C for 50 min in Example 3.

[0029] Fig.11 : HRTEM image of the nanodiamond / graphene composite thin film electrode NCD-G-50 thermally oxidized at 600°C for 50 min in Example 3.

[0030] Fig.12 : The nanodiamond / graphene composite film electrode NCD-G-50 thermally oxidized at 600 °C for 50 min in Example 3 has a wave number of (a) 800-2200 cm -1 and (b) 2200-3500 cm -1 Raman spectrum of .

[0031] Fig.13 : The nanodiamond / graphene composite film electrode NCD-G-50 thermally oxidized at 600 °C for 50 min in Example 3 is (a) 0.5 MH 2 SO 4 and (b) 1 M KCl + 1 mM K 3 Fe(CN) 6 CV curves in electrolyte at a scan rate of 100 mV / s.

[0032] Fig.14 : The nanodiamond / graphene composite film electrode NCD-G-50 thermally oxidized at 600°C for 50 min in Example 3 was heated to 0.5 MH 2 SO 4(a) Polarization curve and (b) Tafel slope plot of LSV test at a scan rate of 100 mV / s in electrolyte.

[0033] Fig.15 : FESEM image of the nanodiamond / graphene composite thin film electrode NCD-G in Comparative Example 1.

[0034] Fig.16 : HRTEM image of the nanodiamond / graphene composite thin film electrode NCD-G in Comparative Example 1.

[0035] Fig.17 : The nano-diamond / graphene composite film electrode NCD-G in Comparative Example 1 has a wave number of (a) 800-2200 cm -1 and (b) 2200-3500 cm -1 Raman spectrum of .

[0036] Fig.18 :Comparative Example 1 of the nano-diamond / graphene composite film electrode NCD-G at (a) 0.5 MH 2 SO 4 and (b) 1 M KCl + 1 mM K 3 Fe(CN) 6 CV curves in electrolyte at a scan rate of 100 mV / s.

[0037] Fig.19 : The nano-diamond / graphene composite film electrode NCD-G in Comparative Example 1 was heated to 0.5 MH 2 SO 4 (a) Polarization curve and (b) Tafel slope plot of LSV test at a scan rate of 100 mV / s in electrolyte. DETAILED DESCRIPTION

[0038] The present invention is further described below by means of specific embodiments, but the protection scope of the present invention is not limited thereto.

[0039] In the following examples, the diamond powder is HFD-PB diamond powder with a particle size of 500 nm produced by Zhecheng Huifeng Diamond Technology Co., Ltd.

[0040] The single crystal silicon wafer is P-type produced by Zhejiang Lijing Silicon Materials Co., Ltd. <100> Single crystal single-sided polished silicon wafer, the diameter of the silicon wafer is 100 ± 0.4 mm, and the silicon wafer is cut into 20×20 mm size when used;

[0041] The hot-wire chemical vapor deposition equipment was developed by Shanghai Jiao Tong University, model JUHFCVD001;

[0042] The muffle furnace was developed by Hefei Kejing Material Technology Co., Ltd. and its model is KSL-1200X.

[0043] Example 1

[0044] Diamond powder with a particle size of 500 nm and deionized water are mixed evenly in a ratio of 1 g: 100 ml, and the mixed solution is placed in an ultrasonic cleaner for 20 minutes to evenly disperse the diamond powder in the solution to obtain a diamond seed solution; the diamond seed solution is taken on a polishing flannel cloth, and a single crystal silicon wafer is ground back and forth at the seed solution for 20 minutes to grind the seed crystal, and then the ground seeded single crystal silicon wafer is placed in the diamond seed solution for ultrasonic seeding for 30 minutes, and then the obtained single crystal silicon wafer is washed with deionized water and blown dry with nitrogen to finally obtain a seeded single crystal silicon wafer.

[0045] The seeded single crystal silicon wafer was placed as a substrate in a hot wire chemical vapor deposition device, tantalum wire was used as the metal wire, acetone was used as the carbon source, the acetone was brought into the reaction chamber by bubbling high-purity hydrogen with a flow rate of 80 sccm, and high-purity hydrogen with a flow rate of 200 sccm was also introduced, the growth power was controlled to be 2200 W, the growth pressure was 1.0 kPa, and the growth time of the nano diamond layer was 90 min; after the growth was completed, the acetone was stopped, and the voltage was slowly reduced to 0 V at a rate of 1 V / min in a high-purity hydrogen atmosphere so that the growth power was reduced to 0 W, thereby obtaining a nano diamond / graphene composite thin film electrode, which was named NCD-G.

[0046] The nanodiamond / graphene composite thin film electrode NCD-G was then placed in a muffle furnace, the temperature was controlled at 600°C, and the treatment time was 10 min. A nanodiamond / graphene composite thin film electrode with both high hydrogen evolution potential and high electrochemical activity was obtained, which was named NCD-G-10.

[0047] Field emission scanning electron microscopy (FESEM) was used to observe the surface morphology of NCD-G-10. Microscopic confocal laser Raman spectrometer (Raman) was used to detect the phase composition of NCD-G-10. Electrochemical workstation was used to detect the electrochemical properties of NCD-G-10.

[0048] Figure 1 The FESEM image of the nanodiamond / graphene composite film electrode NCD-G-10 thermally oxidized at 600 °C for 10 min at 100,000 times magnification. From the image, it can be observed that the NCD-G-10 composite film electrode is composed of a continuous accumulation of large spherical particles covered by a large number of angular flake-like small particles on the surface.

[0049] Figure 2 Raman spectrum of nanodiamond / graphene composite film electrode NCD-G-10 thermally oxidized at 600 °C for 10 min. Figure 2 (a) consists of 1140, 1250, 1332, 1350, 1470, 1580 and 1620 cm -1 The seven characteristic peaks indicate the surface structural characteristics of the nano-diamond composite film. -1 and 1470 cm -1 The peak at is attributed to the sp 2 CC vibration, 1250 cm -1 The peak at 1332 cm is caused by the broadened vibrational density of states of diamond clusters with smaller grain size and tetrahedral amorphous carbon. -1 The peak at 1350 cm is a typical diamond characteristic peak. -1 The D peak at the graphite grain boundary is disordered or other structural defects at the sp 2 Bond stretching vibration related, 1580 cm -1 The G peak at is caused by the sp 2 Hybridized CC bond vibration, 1620 cm -1 The peak at is the D' peak associated with graphene edge states and defects. Figure 2 In (b), 2700 and 2950 cm -1 There are two characteristic peaks, which correspond to the 2D peak of the double frequency Raman characteristics of the complete dispersion of phonons related to single-layer or few-layer graphene and the D+D' peak related to the expression of auxiliary defects. D / I G The value is often used to indicate the degree of defects in the graphite phase in thin film electrodes. D / I G The larger the value, the greater the degree of defects in the graphite phase in the thin film electrode; the half-peak width of the G peak can reflect the distortion of the bond length and bond angle of graphite, and is often used to indicate the degree of order of graphite inside the thin film electrode. Generally, the smaller the half-peak width of the G peak, the higher the degree of order of graphite inside the thin film electrode; D’ / I G The value is mainly used to indicate the defect content of graphene edge in thin film electrodes. D’ / I G The larger the value, the more defects there are at the edge of graphene in the thin film electrode; 2D / I G The value is mainly used to indicate the change of graphite layer number. 2D / I GThe larger the value, the fewer graphite layers, and the closer it is to the structure of single-layer graphene; the half-peak width of the 2D peak is often used to indicate the degree of order of graphene in thin-film electrodes. Generally, the smaller the half-peak width of the 2D peak, the higher the degree of order of graphene inside the thin-film electrode. Figure 2 In (a) and (b), the I of NCD-G-10 can be calculated. D / I G The value is 1.73, and the half-peak width of the G peak is 92.566 cm -1 , I D’ / I G The value is 0.44, I 2D / I G The value of is 0.27, and the half-peak width of the 2D peak is 167.98 cm -1 .

[0050] Figure 3 (a) and (b) are the nanodiamond / graphene composite film electrode NCD-G-10 thermally oxidized at 600 °C for 10 min at 0.5 MH 2 SO 4 and 1 M KCl + 1 mM K 3 Fe(CN) 6 CV curves in electrolyte at a scan rate of 100 mV / s; Figure 3 From (a), we can see that the potential window of NCD-G-10 is 3.43 V (vs SCE), and the hydrogen evolution potential is -1.64 V (vs SCE). The reference electrode is converted from the saturated calomel electrode (SCE) used in the experiment of the present invention to the reversible hydrogen electrode (RHE), and its hydrogen evolution potential is -1.88 V (vs RHE). Figure 3 (b) shows that the electrochemical active area C of NCD-G-10 A 1526.5 μC / cm 2 Compared with NCD-G in Comparative Example 1, the hydrogen evolution potential and electrochemical active area of ​​NCD-G-10 are slightly higher, its hydrogen evolution potential is negatively shifted by about 0.03 V, and the electrochemical active area is increased by about 1.7 times, indicating that thermal oxidation treatment for 10 minutes can slightly improve the electrochemical related properties of nanodiamond-based thin film electrodes.

[0051] Figure 4 (a) and (b) are the nanodiamond / graphene composite film electrode NCD-G-10 thermally oxidized at 600 °C for 10 min at 0.5 MH 2 SO 4 Polarization curve and Tafel slope diagram of LSV test in electrolyte at a scan rate of 100 mV / s. Figure 4In (a), it can be seen that NCD-G-10 has a current density of 10 mA / cm 2 The overpotential for hydrogen evolution is -1.50 V (vs SCE), and the reference electrode is converted from the saturated calomel electrode (SCE) used in the experiment of the present invention to the reversible hydrogen electrode (RHE), whose overpotential for hydrogen evolution is -1.74 V (vs RHE); Figure 4 In (b), it can be seen that the Tafel slope of NCD-G-10 is 420 mV / dec. Therefore, compared with NCD-G in Comparative Example 1, NCD-G-10 has a higher current density of 10 mA / cm 2 The hydrogen evolution overpotential and Tafel slope increased slightly, so the hydrogen evolution potential of NCD-G-10 also increased slightly.

[0052] Example 2

[0053] Diamond powder with a particle size of 500 nm and deionized water are mixed evenly in a ratio of 1 g: 100 ml, and the mixed solution is placed in an ultrasonic cleaner for 20 minutes to evenly disperse the diamond powder in the solution to obtain a diamond seed solution; the diamond seed solution is taken on a polishing flannel cloth, and a single crystal silicon wafer is ground back and forth at the seed solution for 20 minutes to grind the seed crystal, and then the ground seeded single crystal silicon wafer is placed in the diamond seed solution for ultrasonic seeding for 30 minutes, and then the obtained single crystal silicon wafer is washed with deionized water and blown dry with nitrogen to finally obtain a seeded single crystal silicon wafer.

[0054] The seeded single crystal silicon wafer was placed as a substrate in a hot wire chemical vapor deposition device, tantalum wire was used as the metal wire, acetone was used as the carbon source, the acetone was brought into the reaction chamber by bubbling high-purity hydrogen with a flow rate of 80 sccm, and high-purity hydrogen with a flow rate of 200 sccm was also introduced, the growth power was controlled to be 2200 W, the growth pressure was 1.0 kPa, and the growth time of the nano diamond layer was 90 min; after the growth was completed, the acetone was stopped, and the voltage was slowly reduced to 0 V at a rate of 1 V / min in a high-purity hydrogen atmosphere so that the growth power was reduced to 0 W, thereby obtaining a nano diamond / graphene composite thin film electrode, which was named NCD-G.

[0055] The nanodiamond / graphene composite thin film electrode NCD-G was then placed in a muffle furnace, the temperature was controlled at 600°C, and the treatment time was 30 min. A nanodiamond / graphene composite thin film electrode with both high hydrogen evolution potential and high electrochemical activity was obtained, which was named NCD-G-30.

[0056] Field emission scanning electron microscopy (FESEM) was used to observe the surface morphology of NCD-G-30; high resolution electron microscopy (HRTEM) was used to observe the microstructure of NCD-G-30; microscopic confocal laser Raman spectrometer (Raman) was used to detect the phase composition of NCD-G-30; and electrochemical workstation was used to detect the electrochemical related properties of NCD-G-30.

[0057] Figure 5 The FESEM image of the nanodiamond / graphene composite film electrode NCD-G-30 thermally oxidized at 600 °C for 30 min at 100,000 times magnification. Figure 5 It can be observed that the NCD-G-30 composite thin film electrode is composed of many large spherical particles connected together, and there are many small particles with irregular shapes on the surface of the large spherical particles.

[0058] Figure 6 HRTEM image of nanodiamond / graphene composite film electrode NCD-G-30 thermally oxidized at 600 °C for 30 min. Figure 6 Fast Fourier transform was performed on (a) and local areas (a1) and (a2), and diffraction points of the diamond (111) crystal plane with a crystal plane angle of 70° and the graphite (101) crystal plane were observed. A small amount of graphite fringes and twin diamond lattice fringes were observed in (a1). A small amount of graphite fringes corresponded to the graphite (101) crystal plane with a crystal plane spacing of 0.203 nm, and the twin diamond fringes corresponded to the diamond (111) crystal plane with a crystal plane spacing of 0.206 nm; graphite and twin diamond with the same crystal plane were also observed in (a2). Figure 6 Fast Fourier transform of the local area (b1) in (b) also reveals the diffraction points of the graphite (111) and (101) crystal planes. From (b1), we can see the structure of the graphite-coated nanodiamond with thin, short and orderly layers. Figure 6 In (a) and (b), red represents diamond. From the red area in the figure, it can be seen that the diamond grains of the composite thin film electrode NCD-G-30 are larger in size and more concentrated in distribution area.

[0059] Figure 7 Raman spectrum of nanodiamond / graphene composite film electrode NCD-G-30 thermally oxidized at 600 °C for 30 min. Figure 7 (a) consists of 1140, 1250, 1332, 1350, 1470, 1580 and 1620 cm -1 The seven characteristic peaks indicate the surface structural characteristics of the nano-diamond composite film. -1and 1470 cm -1 The peak at is attributed to the sp 2 CC vibration, 1250 cm -1 The peak at 1332 cm is caused by the broadened vibrational density of states of diamond clusters with smaller grain size and tetrahedral amorphous carbon. -1 The peak at 1350 cm is a typical diamond characteristic peak. -1 The D peak at the graphite grain boundary is disordered or other structural defects at the sp 2 Bond stretching vibration related, 1580 cm -1 The G peak at is caused by the sp 2 Hybridized CC bond vibration, 1620 cm -1 The peak at is the D' peak associated with graphene edge states and defects. Figure 7 In (b), 2700 and 2950 cm -1 There are two characteristic peaks, corresponding to the 2D peak of the double frequency Raman characteristics of the complete dispersion of phonons related to single-layer or few-layer graphene and the D+D' peak related to the expression of auxiliary defects. Figure 7 In (a) and (b), the I of NCD-G-30 can be calculated. D / I G The value of is 1.97, and the half-peak width of the G peak is 68.137 cm -1 , I D’ / I G The value is 1.03, I 2D / I G The value of is 0.50, and the half-peak width of the 2D peak is 92.47 cm -1 .

[0060] Figure 8 (a) and (b) are the nanodiamond / graphene composite film electrode NCD-G-30 thermally oxidized at 600 °C for 30 min at 0.5 MH 2 SO 4 and 1 M KCl + 1 mM K 3 Fe(CN) 6 CV curves in electrolyte at a scan rate of 100 mV / s; Figure 8 From (a), we can see that the potential window of NCD-G-30 is 3.82 V (vs SCE), and the hydrogen evolution potential is -1.98 V (vs SCE). The reference electrode is converted from the saturated calomel electrode (SCE) used in the experiment of the present invention to the reversible hydrogen electrode (RHE), and its hydrogen evolution potential is -2.22 V (vs RHE). Figure 8(b) shows that the electrochemical active area C of NCD-G-30 A 4462.3 μC / cm 2 Compared with NCD-G in Comparative Example 1, the hydrogen evolution potential and electrochemical active area of ​​NCD-G-30 are significantly increased, with its hydrogen evolution potential shifted negatively by about 0.37 V and its electrochemical active area increased by about 5 times, indicating that thermal oxidation treatment for 30 min can significantly improve the electrochemical related properties of nanodiamond-based thin film electrodes.

[0061] Fig. 9 (a) and (b) are the nanodiamond / graphene composite film electrode NCD-G-30 thermally oxidized at 600 °C for 30 min at 0.5 MH 2 SO 4 Polarization curve and Tafel slope diagram of LSV test in electrolyte at a scan rate of 100 mV / s. Fig. 9 In (a), it can be seen that NCD-G-30 has a current density of 10 mA / cm 2 The overpotential for hydrogen evolution is -1.90 V (vs SCE), and the reference electrode is converted from the saturated calomel electrode (SCE) used in the experiment of the present invention to the reversible hydrogen electrode (RHE), whose overpotential for hydrogen evolution is -2.14 V (vs RHE); Fig. 9 In (b), it can be seen that the Tafel slope of NCD-G-30 is 619 mV / dec. Compared with NCD-G in Comparative Example 1, NCD-G-30 has a higher current density of 10 mA / cm 2 The hydrogen evolution overpotential and Tafel slope increased significantly, so the hydrogen evolution potential of NCD-G-30 also increased significantly.

[0062] Example 3

[0063] Diamond powder with a particle size of 500 nm and deionized water are mixed evenly in a ratio of 1 g: 100 ml, and the mixed solution is placed in an ultrasonic cleaner for 20 minutes to evenly disperse the diamond powder in the solution to obtain a diamond seed solution; the diamond seed solution is taken on a polishing flannel cloth, and a single crystal silicon wafer is ground back and forth at the seed solution for 20 minutes to grind the seed crystal, and then the ground seeded single crystal silicon wafer is placed in the diamond seed solution for ultrasonic seeding for 30 minutes, and then the obtained single crystal silicon wafer is washed with deionized water and blown dry with nitrogen to finally obtain a seeded single crystal silicon wafer.

[0064] The seeded single crystal silicon wafer was placed as a substrate in a hot wire chemical vapor deposition device, tantalum wire was used as the metal wire, acetone was used as the carbon source, the acetone was bubbled into the reaction chamber with high-purity hydrogen at a flow rate of 80 sccm, and high-purity hydrogen at a flow rate of 200 sccm was also introduced, the growth power was controlled to be 2200 W, the growth pressure was 1.0 kPa, and the growth time of the nano diamond layer was 90 min; after the growth was completed, the acetone was stopped, and the voltage was slowly reduced to 0 V at a rate of 1 V / min in a high-purity hydrogen atmosphere, so that the growth power was reduced to 0 W, and a nano diamond / graphene composite thin film electrode was obtained, which was named NCD-G.

[0065] The nanodiamond / graphene composite thin film electrode NCD-G was then placed in a muffle furnace, the temperature was controlled at 600°C, and the treatment time was 50 min. A nanodiamond / graphene composite thin film electrode with both high hydrogen evolution potential and high electrochemical activity was obtained, which was named NCD-G-50.

[0066] Field emission scanning electron microscopy (FESEM) was used to observe the surface morphology of NCD-G-50; high resolution electron microscopy (HRTEM) was used to observe the microstructure of NCD-G-50; microscopic confocal laser Raman spectrometer (Raman) was used to detect the phase composition of NCD-G-50; and electrochemical workstation was used to detect the electrochemical related properties of NCD-G-50.

[0067] Fig.10 The FESEM image of the nanodiamond / graphene composite film electrode NCD-G-50 thermally oxidized at 600 °C for 50 min at 100,000 times magnification. Fig.10 It can be observed that NCD-G-50 is composed of large spherical particles with a cauliflower-like surface morphology, and there are many tiny holes and gaps on the surface of the large spherical particles.

[0068] Fig.11 HRTEM image of nanodiamond / graphene composite film electrode NCD-G-50 thermally oxidized at 600 °C for 50 min. Fig.11 Fast Fourier transform was performed on (a) and local areas (a1) and (a2), and diffraction points of the diamond (111) crystal plane with a crystal plane angle of 70° and the graphite (101) and (100) crystal planes were observed. (a1) shows a large number of lattice fringes of the diamond (111) crystal plane with a crystal plane spacing of 0.206 nm, and a small amount of lattice fringes of the graphite (100) crystal plane and the diamond (111) crystal plane can be observed in (a2). Fig.11Fast Fourier transform was performed on (b) and local areas (b1) and (b2), and diffraction points of diamond (111) crystal plane, graphite (101) and (002) crystal plane were observed. The lattice fringes of diamond (111) crystal plane and graphite (002) crystal plane can be observed from (b1) and (b2). The fringes of graphite are long and orderly, and the number of layers is small, showing the morphology of few-layer graphene. Fig.11 In (a) and (b), red represents diamond. From the red area in the figure, it can be seen that the size of the diamond grains in the NCD-G-50 composite thin film electrode is smaller than that of the NCD-G in Comparative Example 1, and the distribution area is more uniform.

[0069] Fig.12 Raman spectrum of nanodiamond / graphene composite film electrode NCD-G-50 thermally oxidized at 600 °C for 50 min. Fig.12 (a) consists of 1140, 1250, 1332, 1350, 1470, 1580 and 1620 cm -1 The seven characteristic peaks indicate the surface structural characteristics of the nano-diamond composite film. -1 and 1470 cm -1 The peak at is attributed to the sp 2 CC vibration, 1250 cm -1 The peak at 1332 cm is caused by the broadened vibrational density of states of diamond clusters with smaller grain size and tetrahedral amorphous carbon. -1 The peak at 1350 cm is a typical diamond characteristic peak. -1 The D peak at the graphite grain boundary is disordered or other structural defects at the sp 2 Bond stretching vibration related, 1580 cm -1 The G peak at is caused by the sp 2 Hybridized CC bond vibration, 1620 cm -1 The peak at is the D' peak associated with graphene edge states and defects. Fig.12 In (b), 2700 and 2950 cm -1 There are two characteristic peaks, corresponding to the 2D peak of the double frequency Raman characteristics of the complete dispersion of phonons related to single-layer or few-layer graphene and the D+D' peak related to the expression of auxiliary defects. Fig.12 In (a) and (b), the I of NCD-G-50 can be calculated. D / I G The value of is 2.85, and the half-peak width of the G peak is 51.24 cm -1 , I D’ / IG The value is 1.68, I 2D / I G The value of is 0.42, and the half-peak width of the 2D peak is 90.89 cm -1 .

[0070] Fig.13 (a) and (b) are the nanodiamond / graphene composite film electrode NCD-G-50 thermally oxidized at 600 °C for 50 min at 0.5 MH 2 SO 4 and 1 mM KCl + 1 mM K 3 Fe(CN) 6 CV curves in electrolyte at a scan rate of 100 mV / s; Fig.13 In (a), the potential window of NCD-G-50 is 3.66 V (vs SCE), and the hydrogen evolution potential is -1.74 V (vs SCE). The reference electrode is converted from the saturated calomel electrode (SCE) used in the experiment of the present invention to the reversible hydrogen electrode (RHE), and its hydrogen evolution potential is -1.98 V (vs RHE). Fig.13 (b) The electrochemical active area C of NCD-G-50 can be obtained A 5324.1 μC / cm 2 Compared with NCD-G in Comparative Example 1, the hydrogen evolution potential and electrochemical active area of ​​NCD-G-50 are significantly increased, with its hydrogen evolution potential shifted negatively by about 0.13 V and its electrochemical active area increased by about 6 times, indicating that thermal oxidation treatment for 50 min can significantly improve the electrochemical related properties of nanodiamond-based thin film electrodes.

[0071] Fig.14 (a) and (b) are the nanodiamond / graphene composite film electrode NCD-G-50 thermally oxidized at 600 °C for 50 min and heated to 0.5 MH 2 SO 4 Polarization curve and Tafel slope diagram of LSV test in electrolyte at a scan rate of 100 mV / s; Fig.14 In (a), it can be seen that NCD-G-50 has a current density of 10 mA / cm 2 The overpotential for hydrogen evolution is -1.45 V (vs SCE), and the reference electrode is converted from the saturated calomel electrode (SCE) used in the experiment of the present invention to the reversible hydrogen electrode (RHE), whose overpotential for hydrogen evolution is -1.69 V (vs RHE); Fig.14In (b), it can be seen that the Tafel slope of NCD-G-50 is 468 mV / dec; compared with NCD-G in Comparative Example 1, the hydrogen evolution overpotential of NCD-G-50 is slightly reduced, but its Tafel slope is significantly increased, so the hydrogen evolution potential of NCD-G-50 can be increased.

[0072] Comparative Example 1

[0073] Diamond powder with a particle size of 500 nm and deionized water are mixed evenly in a ratio of 1 g: 100 ml, and the mixed solution is placed in an ultrasonic cleaner for 20 minutes to evenly disperse the diamond powder in the solution to obtain a diamond seed solution; the diamond seed solution is taken on a polishing flannel cloth, and a single crystal silicon wafer is ground back and forth at the seed solution for 20 minutes to grind the seed crystal, and then the ground seeded single crystal silicon wafer is placed in the diamond seed solution for ultrasonic seeding for 30 minutes, and then the obtained single crystal silicon wafer is washed with deionized water and blown dry with nitrogen to finally obtain a seeded single crystal silicon wafer.

[0074] The seeded single crystal silicon wafer was placed as a substrate in a hot wire chemical vapor deposition device, tantalum wire was used as the metal wire, acetone was used as the carbon source, the acetone was brought into the reaction chamber by bubbling high-purity hydrogen with a flow rate of 80 sccm, and high-purity hydrogen with a flow rate of 200 sccm was also introduced, the growth power was controlled to be 2200 W, the growth pressure was 1.0 kPa, and the growth time of the nano diamond layer was 90 min; after the growth was completed, the acetone was stopped, and the voltage was slowly reduced to 0 V at a rate of 1 V / min in a high-purity hydrogen atmosphere so that the growth power was reduced to 0 W, thereby obtaining a nano diamond / graphene composite thin film electrode, which was named NCD-G.

[0075] Field emission scanning electron microscopy (FESEM) was used to observe the surface morphology of NCD-G; high resolution electron microscopy (HRTEM) was used to observe the microstructure of NCD-G; microscopic confocal laser Raman spectrometer (Raman) was used to detect the phase components of NCD-G; and an electrochemical workstation was used to detect the electrochemical related properties of NCD-G.

[0076] Fig.15 This is a FESEM image of the nanodiamond / graphene composite film electrode NCD-G at 100,000 times magnification. From the image, it can be observed that the NCD-G composite film electrode is composed of continuous accumulation of spherical particles, and the surface of the large spherical particles is covered by a large number of angular lamellar particles and small spherical particles.

[0077] Fig.16 This is the HRTEM image of the nanodiamond / graphene composite film electrode NCD-G. Fig.16Fast Fourier transform is performed on (a) and local areas (a1) and (a2), and diffraction points of diamond (111) crystal plane, graphite (002) and (101) crystal plane can be observed. From (a1), stripes of graphite (002) crystal plane with a crystal plane spacing of 0.337 nm and graphite (101) crystal plane with a crystal plane spacing of 0.203 nm can be observed. These graphite stripes have more layers and are more twisted. From (a2), stripes of graphite (101) crystal plane with more layers and twisted disorder can be observed, and a few lattice stripes of diamond (111) crystal plane with a crystal plane spacing of 0.206 nm can be observed at the edges of these graphite stripes. Fig.16 Fast Fourier transform was performed on (b) and local areas (b1) and (b2), and diffraction points of diamond (111) crystal plane and graphite (004) crystal plane were observed. Many lattice fringes of graphite (004) crystal plane with a lattice spacing of 0.168 nm were observed from (b1). These graphite fringes were thick and curved, and nanodiamond particles covered by graphite could be observed from (b2). Fig.16 (a) and (b) are dyed. The red dyed area in the figure represents the distribution and size of diamonds. It can be seen that the diamond size is 3~5 nm, the distribution area is small, and the amorphous phase component is large.

[0078] Fig.17 This is the Raman spectrum of nanodiamond / graphene composite thin film electrode NCD-G. Fig.17 (a) consists of 1140, 1250, 1332, 1350, 1470, 1580 and 1620 cm -1 There are seven characteristic peaks, among which 1140 cm -1 and 1470 cm -1 The peak at is attributed to the sp 2 CC vibration, 1250 cm -1 The peak at 1332 cm is caused by the broadened vibrational density of states of diamond clusters with smaller grain size and tetrahedral amorphous carbon. -1 The peak at 1350 cm is a typical diamond characteristic peak. -1 The D peak at the graphite grain boundary is disordered or other structural defects at the sp 2 Bond stretching vibration related, 1580 cm -1 The G peak at is caused by the sp 2 Hybridized CC bond vibration, 1620 cm -1 The peak at is the D' peak associated with graphene edge states and defects. Fig.17In (b), 2700 and 2950 cm -1 There are two characteristic peaks, corresponding to the 2D peak of the double frequency Raman characteristics of the complete dispersion of phonons related to single-layer or few-layer graphene and the D+D' peak related to the expression of auxiliary defects. Fig.17 In (a) and (b), the I of NCD-G can be calculated. D / I G The value is 1.58, and the half-peak width of the G peak is 97.46 cm -1 , I D’ / I G The value is 0.29, I 2D / I G The value is 0.26, and the half-peak width of the 2D peak is 306.33 cm -1 .

[0079] Fig.18 (a) and (b) are nanodiamond / graphene composite film electrode NCD-G at 0.5 MH 2 SO 4 and 1 M KCl + 1 mM K 3 Fe(CN) 6 CV curves in electrolyte at a scan rate of 100 mV / s; Fig.18 As shown in (a), the potential window of NCD-G is 3.35 V (vs SCE), and the hydrogen evolution potential is -1.61 V (vs SCE). The reference electrode is converted from the saturated calomel electrode (SCE) used in the experiment of the present invention to the reversible hydrogen electrode (RHE), and its hydrogen evolution potential is -1.85 V (vs RHE). Fig.18 (b) shows that the electrochemical active area C of NCD-G A 880.8 μC / cm 2 .

[0080] Fig.19 (a) and (b) are nanodiamond / graphene composite film electrode NCD-G at 0.5 MH 2 SO 4 Polarization curve and Tafel slope diagram of LSV test in electrolyte at a scan rate of 100 mV / s; Fig.19 In (a), it can be seen that NCD-G has a current density of 10 mA / cm 2 The overpotential for hydrogen evolution is -1.47 V (vs SCE), and the reference electrode is converted from the saturated calomel electrode (SCE) used in the experiment of the present invention to the reversible hydrogen electrode (RHE), whose overpotential for hydrogen evolution is -1.71 V (vs RHE); Fig.19In (b), we can see that the Tafel slope of NCD-G is 307 mV / dec.

Claims

1. A nanodiamond / graphene composite film electrode having both high hydrogen evolution potential and high electrochemical activity, characterized in that: Prepared as follows: (1) Pre-treating a single crystal silicon wafer with a diamond seeding liquid to obtain a seeded single crystal silicon wafer; (2) using the seeded single crystal silicon wafer obtained in step (1) as a substrate, and preparing a continuous and dense nanodiamond / graphene composite thin film electrode by hot wire chemical vapor deposition; The operation is as follows: a single crystal silicon wafer after seeding is placed in a hot wire chemical vapor deposition device, a tantalum wire is used as a metal wire, acetone is used as a carbon source, acetone is brought into the reaction chamber by bubbling high-purity hydrogen with a flow rate of 80 sccm, and high-purity hydrogen with a flow rate of 200 sccm is also introduced, the growth power is controlled to be 2200 W, the growth pressure is 1.0 kPa, and the growth time is 90 min. After the growth is completed, the acetone is stopped, and the voltage is reduced to 0 V at a rate of 1 V / min in a high-purity hydrogen atmosphere, so that the power is reduced to 0 W, and a nano-diamond / graphene composite thin film electrode is obtained; (3) placing the nanodiamond / graphene composite thin film electrode prepared in step (2) in a muffle furnace for thermal oxidation treatment to obtain the nanodiamond / graphene composite thin film electrode having both high hydrogen evolution potential and high electrochemical activity; Set the muffle furnace temperature to 500-700 °C and the thermal oxidation treatment time to 10-50 min.

2. The nanodiamond / graphene composite film electrode having both high hydrogen evolution potential and high electrochemical activity as claimed in claim 1, characterized in that: In step (1), the preparation method of diamond seed solution is as follows: diamond powder is mixed with deionized water, and ultrasonically dispersed to obtain a diamond seed solution.

3. The nanodiamond / graphene composite film electrode having both high hydrogen evolution potential and high electrochemical activity as claimed in claim 2, characterized in that: The mass volume ratio of diamond powder to deionized water is 1:100, g / mL.

4. The nanodiamond / graphene composite film electrode having both high hydrogen evolution potential and high electrochemical activity as claimed in claim 1, characterized in that: In step (1), the seeding operation is as follows: take diamond seeding liquid on the polishing flannel, grind the single crystal silicon wafer back and forth at the seeding liquid to grind the seeding crystal, and the grinding time is 20 minutes; then place the single crystal silicon wafer after the seeding crystal is ground in the diamond seeding liquid, and ultrasonic seeding is performed for 30 minutes; then take out the single crystal silicon wafer, wash it with deionized water, and blow it dry with nitrogen to obtain the single crystal silicon wafer after seeding.

5. The nanodiamond / graphene composite film electrode having both high hydrogen evolution potential and high electrochemical activity as claimed in claim 1, characterized in that: In step (3), the muffle furnace temperature is set to 600°C and the thermal oxidation treatment time is 30-40 min.

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