A nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material and its preparation method and application

Abstract

The present invention belongs to the technical field of capacitor materials, and specifically relates to a nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material, its preparation method, and application. The preparation method of the composite material described in the present invention comprises the following steps: preparing NiO powder, dissolving it in water, applying it to an FTO electrode, and drying it to obtain a NiO electrode; then adding 9-hydroxyfluorene and tetrabutylammonium boron tetrafluoride to acetonitrile, and adding trifluoroacetic acid to obtain an electrolyte; and obtaining a nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material loaded on the electrode by electrochemical polymerization; the electrochemical polymerization is carried out by a constant potential method, with the NiO electrode, Pt wire, and Ag / AgCl serving as the working electrode, counter electrode, and reference electrode, respectively. The preparation method of the nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material provided by the present invention is simple to operate, and the prepared composite material is applied to supercapacitor conductive materials to improve charge storage performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of capacitor materials, and in particular relates to a nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material and a preparation method and application thereof. Background Art

[0002] Currently, secondary batteries and supercapacitors are considered to be the most promising candidate materials for widespread use in energy storage applications. Although secondary batteries can provide higher energy density, they still have obvious disadvantages such as low power density and a longer energy storage process. As a new type of energy storage device, supercapacitors have the advantages of fast charging and discharging speed, high power density, long cycle life, and eco-friendliness. These characteristics make them very promising for application in portable electronics, electric vehicles, and various energy storage applications. Compared with traditional capacitors, supercapacitor electrodes can produce ultra-high capacitance and energy density. Compared with secondary batteries, supercapacitors can store electrical energy through double-layer charge adsorption near the surface or Faradaic redox reactions, so supercapacitors have both higher power density and higher energy storage capacity. Therefore, supercapacitors are attracting more and more attention from researchers.

[0003] As a crucial component of supercapacitors, electrode materials' charge storage properties directly determine their energy storage capacity. Currently studied supercapacitor electrode materials primarily include carbon materials, conductive polymers, and transition metal oxides. Nickel oxide (NiO), a typical transition metal oxide electrode material for supercapacitors, has attracted considerable attention due to its high specific capacity and excellent electrochemical properties. However, its poor cycling stability and low electrical conductivity make it a practical electrode material. To address the major challenges inherent in NiO, researchers have employed strategies such as microstructure adjustment, doping with other metal elements, and composites with other metal oxides to enhance its supercapacitive performance. While significant progress has been made in the development of nickel-based electrode materials as supercapacitor electrodes, the current challenge is that the actual specific capacity remains low, particularly at high current densities and during charge-discharge cycling. This is due to NiO's poor conductivity, which hinders the rapid transfer of electrons to participate in electrode reactions during charge-discharge cycles, leading to increased electrode polarization.

[0004] Conductive polymers are widely used in supercapacitors due to their excellent electrical conductivity and electrochemical redox reversibility. In particular, due to their excellent electrical conductivity and pseudocapacitive properties, many studies have reported significantly improved charge storage performance in composite electrode materials prepared by combining conductive polymers with NiO as the conductive layer. In recent years, fluorene-based conductive polymers have been widely used in electronic devices such as blue light-emitting diodes, organic lasers, and field-effect transistors due to their ease of modification, blue light emission, and high fluorescence quantum efficiency. Some studies have demonstrated that polyfluorene materials also exhibit excellent pseudocapacitive properties. Tailoring the substitution of functional groups at the C-9 position of polyfluorene materials is an effective strategy for controlling material properties. However, these polyfluorene derivatives require high oxidation potentials for polymerization, which can disrupt the conjugated structure of the polymer and reduce its performance. 9-Hydroxyfluorene, due to the p-π coupling of the electron-donating hydroxyl group in its structure, also has a low electrochemical oxidation potential, making it difficult to use as capacitor electrode materials and improve its performance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing a nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material. The method is simple to operate. The prepared nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material is applied to supercapacitor conductive materials to improve charge storage performance.

[0006] The preparation method of the nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material of the present invention comprises the following steps: first, preparing NiO powder, then dissolving the NiO powder in water, applying the powder to an FTO electrode, and drying the NiO electrode; then, adding 9-hydroxyfluorene and tetrabutylammonium boron tetrafluoride to acetonitrile, and then adding trifluoroacetic acid to obtain an electrolyte; and finally, performing electrochemical polymerization to obtain the nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material loaded on the electrode; the electrochemical polymerization is performed using a constant potential method.

[0007] The electrochemical polymerization uses NiO electrode, Pt wire and Ag / AgCl as working electrode, counter electrode and reference electrode respectively.

[0008] The specific steps for preparing NiO powder are as follows: first, nickel sulfate, acrylamide, and hexamethylenetetramine are dissolved in deionized water at room temperature, and then the obtained acrylamide solution and hexamethylenetetramine solution are added to the nickel sulfate solution in sequence. The obtained mixed solution is hydrothermally reacted at 160-190°C for 4-8 hours, cooled to room temperature, centrifuged, and the obtained precipitate is washed and dried in an oven at 60-90°C for 4-7 hours to obtain Ni(OH)2. Finally, it is annealed at 250-400°C to obtain NiO powder.

[0009] First, 0.15-0.2 g of nickel sulfate, 0.02-0.04 g of acrylamide, and 0.15-0.25 g of hexamethylenetetramine were dissolved in 18-25 mL of deionized water at room temperature.

[0010] Then, 40-60 mg of NiO powder was dissolved in 0.8-1.5 mL of water and dispersed by ultrasonic. 90-120 μL of the solution was applied to the FTO electrode and dried at 180-220° C. for 1.5-2.5 h.

[0011] 9-hydroxyfluorene and tetrabutylammonium boron tetrafluoride are added to acetonitrile so that the concentration of 9-hydroxyfluorene in acetonitrile is 0.8-1.5 mol / L and the concentration of tetrabutylammonium boron tetrafluoride in acetonitrile is 0.08-0.2 mol / L, and trifluoroacetic acid is added so that the trifluoroacetic acid accounts for 12-20% of the volume of the acetonitrile.

[0012] When electrochemical polymerization is performed using a constant potential method, the polymerization potential is 1.0-2.2 V vs. Ag / AgCl, and the polymerization time is 8-12 s.

[0013] A nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material is prepared by the preparation method of the nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material.

[0014] An application of the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material: using the prepared nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material as an anode material and activated carbon as a cathode material to construct an asymmetric supercapacitor.

[0015] The mass ratio of the anode material to the cathode material is 1:1.2~1:2.0.

[0016] Specifically, the preparation method of the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material comprises the following steps:

[0017] (1) Preparation of NiO powder: First, 0.15-0.2g nickel sulfate (NiSO4·5H2O), 0.02-0.04g acrylamide (C3H5NO surfactant), 0.15-0.25g hexamethylenetetramine (C6H 12N4) were dissolved in 18-25 mL of deionized water at room temperature, and then the obtained acrylamide solution and hexamethylenetetramine solution were added to the nickel sulfate solution in sequence, and mixed evenly with a magnetic stirrer. The mixed solution was transferred to a reactor and hydrothermally reacted at 160-190 ° C for 4-8 hours. The reactor was taken out and cooled to room temperature, and centrifuged. The obtained precipitate was washed three times with deionized water and anhydrous ethanol, respectively, and dried in an oven at 60-90 ° C for 4-7 hours to obtain Ni(OH)2. Finally, it was annealed at 250-400 ° C in a muffle furnace to obtain NiO powder.

[0018] (2) Dissolve 40-60 mg of NiO powder in 0.8-1.5 mL of water, disperse it evenly by ultrasonication, apply 90-120 μL of the solution on the FTO electrode, and dry it at 180-220 °C for 1.5-2.5 h to obtain a NiO electrode.

[0019] (3) Add 9-hydroxyfluorene and tetrabutylammonium boron tetrafluoride (Bu4NBF4) to acetonitrile (ACN) so that the concentration of 9-hydroxyfluorene in acetonitrile is 0.8-1.5 mol / L and the concentration of tetrabutylammonium boron tetrafluoride in acetonitrile is 0.08-0.2 mol / L, and then add trifluoroacetic acid (TFA) so that the trifluoroacetic acid accounts for 12-20% of the volume of acetonitrile to obtain an electrolyte.

[0020] (4) Electrochemical polymerization was performed by a constant potential method, with the NiO electrode, Pt wire, and Ag / AgCl prepared in step (2) as the working electrode, counter electrode, and reference electrode, respectively. The polymerization potential was 1.0-2.2 V vs. Ag / AgCl, and the polymerization time was 8-12 s to obtain a nanoflower-like poly(9-hydroxyfluorene) / NiO composite material loaded on the electrode.

[0021] Application of the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material: The prepared nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material is used as an anode material, and activated carbon (AC) is used as a cathode material, so that the mass ratio of the anode material to the cathode material is 1:1.2~1:2.0, to construct an asymmetric supercapacitor.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The method of the present invention is used to prepare a nano-flower-like poly (9-hydroxyfluorene) / NiO composite material, wherein the poly (9-hydroxyfluorene) increases the HOMO energy level and stabilizes the conjugated π bond system, thereby making the composite material have high conductivity and good electrochemical properties.

[0024] (2) The preparation method of the nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material of the present invention is to compound NiO with poly (9-hydroxyfluorene), improve the charge storage performance through the synergistic charge storage effect of poly (9-hydroxyfluorene) and NiO, and realize its application in supercapacitors.

[0025] (3) The nano-flower-like poly (9-hydroxyfluorene) / NiO composite material prepared by the present invention is used to construct an asymmetric supercapacitor and improve the capacitance utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 (A) is a SEM image of the NiO powder prepared in step (1) of Example 1; (B) is a SEM image of the nanoflower-like poly (9-hydroxyfluorene) / NiO composite material prepared in step (4) of Example 1.

[0027] Figure 2 FTIR spectra of the NiO powder prepared in step (1) of Example 1, the nanoflower-shaped poly(9-hydroxyfluorene) / NiO composite material prepared in step (4) of Example 1, and the prepared poly(9-hydroxyfluorene).

[0028] Figure 3 XRD spectra of the NiO powder prepared in step (1) of Example 1 and the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material prepared in step (4) of Example 1.

[0029] Figure 4 (A) is the cyclic voltammogram of the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material prepared in Example 1 at different scan rates, and (B) is the relationship between the peak current density and the scan rate of the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material prepared in Example 1 at different scan rates.

[0030] Figure 5 This is a constant current charge and discharge curve diagram of the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material prepared in Example 1 at different current densities.

[0031] Figure 6 (A) is a cyclic voltammogram of an asymmetric supercapacitor prepared using the nanoflower-shaped poly(9-hydroxyfluorene) / NiO composite material prepared in Example 1 at different scan rates, and (B) is a graph showing the relationship between peak current density and scan rate at different scan rates.

[0032] Figure 7 Graph showing charge and discharge curves of an asymmetric supercapacitor made using the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material prepared in Example 1 at different current densities.

[0033] Figure 83 is a graph showing the relationship between the specific capacitance value and the percentage of the initial capacity retained after 5000 charge and discharge cycles of an asymmetric supercapacitor prepared using the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material prepared in Example 1. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to specific embodiments.

[0035] The raw materials and additives used in the following examples and comparative examples were all commercially available. The volume of the electrolyte in the following examples was mainly sufficient to completely immerse the electrodes.

[0036] Example 1

[0037] The preparation method of the nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material comprises the following steps:

[0038] (1) Preparation of NiO powder: First, 0.156g nickel sulfate (NiSO4·5H2O), 0.03g acrylamide, 0.2g hexamethylenetetramine (C6H 12 N4) were dissolved in 20 mL of deionized water at room temperature, and then the obtained acrylamide solution and hexamethylenetetramine solution were added to the nickel sulfate solution in sequence, mixed evenly with a magnetic stirrer, and the mixed solution was transferred to a reactor and hydrothermally reacted at 180 ° C for 6 h. The reactor was taken out and cooled to room temperature and centrifuged. The obtained precipitate was washed three times with deionized water and anhydrous ethanol respectively, and dried in an oven at 70 ° C for 6 h to obtain Ni(OH)2. Finally, it was annealed at 300 ° C in a muffle furnace to obtain NiO powder, whose SEM image is shown as follows Figure 1 (A) shows its FTIR spectrum. Figure 2 (NiO) is shown in its XRD spectrum. Figure 3 (NiO) shown.

[0039] (2) After dissolving 50 mg of NiO powder in 1.0 mL of water, ultrasonically disperse it evenly, apply 100 μL of the solution on the FTO electrode, and dry it at 200 °C for 2.0 h to obtain a NiO electrode.

[0040] (3) 9-hydroxyfluorene and Bu4NBF4 were added to ACN so that the concentration of 9-hydroxyfluorene in acetonitrile was 1.0 mol / L and the concentration of tetrabutylammonium boron tetrafluoride in acetonitrile was 0.1 mol / L. TFA was then added so that TFA accounted for 15% of the volume of ACN to obtain an electrolyte.

[0041] (4) Electrochemical polymerization was carried out by constant potential method, with the NiO electrode, Pt wire and Ag / AgCl prepared in step (2) as the working electrode, counter electrode and reference electrode, respectively. The polymerization potential was 1.5 V vs. Ag / AgCl, and the polymerization time was 10 s. Nanoflower-like poly (9-hydroxyfluorene) / NiO composite material loaded on the electrode was obtained, and its SEM image is shown in FIG. Figure 1 (B) shows its FTIR spectrum. Figure 2 (PHF / NiO) is shown in its XRD spectrum. Figure 3 The average molecular weight of the poly(9-hydroxyfluorene) in the prepared nanoflower-like poly(9-hydroxyfluorene) / NiO composite material was determined by gel chromatography to be 2400.

[0042] Depend on Figure 1 As can be seen in (A), the NiO powder morphology exhibits a rough surface, similar to flower-like microspheres assembled from nanosheets. This flower-like microsphere structure is conducive to the electrolyte solution penetrating into the interior of the material through the gaps between the nanosheets. Figure 1 (B) shows that poly (9-hydroxyfluorene) is uniformly polymerized on the nanosheet layer on the NiO surface. The poly (9-hydroxyfluorene) / NiO composite material still maintains the flower-like microsphere morphology, but due to the introduction of poly (9-hydroxyfluorene), the sheet thickness increases from the original 13 nm to 20 nm.

[0043] Figure 2 The preparation steps of poly (9-hydroxyfluorene) are as follows: 9-hydroxyfluorene and Bu4NBF4 are added to ACN so that the concentration of 9-hydroxyfluorene in acetonitrile is 1.0 mol / L and the concentration of tetrabutylammonium boron tetrafluoride in acetonitrile is 0.1 mol / L, and then TFA is added so that the volume ratio of TFA to ACN is 15% to obtain an electrolyte. Electrochemical polymerization is carried out by constant potential method, with the FTO electrode, Pt wire and Ag / AgCl in step (2) as the working electrode, counter electrode and reference electrode respectively, the polymerization potential is 1.5 V vs. Ag / AgCl, the polymerization time is 10 s, and poly (9-hydroxyfluorene) loaded on the electrode, namely PHF, is obtained. Its FTIR spectrum is shown in the figure below. Figure 2 As shown in (PHF), the average molecular weight of the detected poly (9-hydroxyfluorene) is 2600.

[0044] from Figure 2 As can be seen from the figure, for NiO, at 3435 cm -1 and 1633 cm -1 The peaks at 400 to 900 cm-1 represent the stretching and bending vibrations of OH, which may be caused by water molecules adsorbed on the NiO surface. -1 The metal oxygen stretching vibration is in the range of 3390 cm-1 The peaks at 824 and 890 cm are related to the stretching vibration of the -OH group. -1 The peak at 1032 cm corresponds to the out-of-plane carbon-hydrogen vibration of the benzene ring, while the peak at 1032 cm -1 The peaks at are related to the in-plane carbon-hydrogen vibrations of the benzene ring. These spectral features are consistent with the spectral features observed in 1,2,4-trisubstituted benzene rings in terms of wavenumber and absorption mode. Therefore, it can be inferred that the polymerization sites of poly(9-hydroxyfluorene) are C(2) and C(7), which is consistent with the polymerization sites of other prepared polyfluorene materials. After the synthesis of poly(9-hydroxyfluorene) and NiO, the characteristic peaks of poly(9-hydroxyfluorene) and NiO appeared in the composite material, indicating that the preparation of poly(9-hydroxyfluorene) / NiO was successful.

[0045] Figure 3 In the XRD spectrum of the NiO crystal, the sharp diffraction peaks at 37.4°, 43.5°, 62.7°, 75.3°, and 79.41° correspond to the (111), (200), (220), (311), and (222) crystal planes of NiO, respectively, according to the standard card (JCPDS 00-047-1049). The diffraction peaks of poly(9-hydroxyfluorene) / NiO are basically consistent with those of NiO. This indicates that poly(9-hydroxyfluorene) has no effect on the crystal structure of NiO, which is caused by the amorphous structure of poly(9-hydroxyfluorene).

[0046] The cyclic voltammetry curves of the nano-flower-like poly (9-hydroxyfluorene) / NiO composite material prepared in this example at different scan rates are as follows: Figure 4 (A) shows the relationship between the peak current density and the scan rate at different scan rates. Figure 4 (B). Figure 4 (A) It can be seen that when the scan rate is changed from 50 mV s -1 Increase to 250 mV s -1 When the scan rate is 0.05, the curve shape does not deform, indicating that the electrode has a good dynamic response and a fast charge transfer rate. At different scan rates, the redox reaction rate on the electrode does not change much, and the influence of polarization and electrolyte diffusion is small. The relationship between the peak current and the scan rate is constructed by the obtained CV curve. Figure 4 (B), The good linear relationship indicates that the capacitive behavior of poly(9-hydroxyfluorene) / NiO is non-diffusion controlled.

[0047] The constant current charge and discharge curves of the nano-flower-like poly (9-hydroxyfluorene) / NiO composite material prepared in this example at different current densities are shown in FIG. Figure 5 As shown. Figure 5 The calculated results show that the composite material has the characteristics of high thermal conductivity, low thermal conductivity and low thermal conductivity at 1, 2, 4, 6, and 8 A g -1The specific capacity values at current densities are 1248, 1160, 976, 852, and 750 F g, respectively. -1 . Generally speaking, the specific capacitance value decreases with increasing current density. This is because at higher current density, the polarization of ion concentration causes the ion transport rate to slow down. The structural changes in the electrode material lead to a decrease in the adsorption and reaction ability of ions, which makes the electrode material unable to fully utilize its storage capacity, resulting in a decrease in specific capacity. On the contrary, at lower current density, the ion transport rate is slower. The ions have enough time to embed and migrate inside the material, and the utilization rate of the active sites inside the electrode material is higher.

[0048] The nanoflower-shaped poly(9-hydroxyfluorene) / NiO composite material prepared in this example was used as the anode material and an activated carbon device as the cathode material, with a mass ratio of 1:1.5, to construct an asymmetric supercapacitor. The commercially available activated carbon device is model XFP01, manufactured by Nanjing Xianfeng Nanomaterial Technology Co., Ltd.

[0049] Among them, the cyclic voltammetry curves of the prepared asymmetric supercapacitor at different scan rates are as follows: Figure 6 (A) shows the relationship between the peak current density and the scan rate at different scan rates. Figure 6 (B) As shown in the figure, the asymmetric supercapacitor does not exhibit obvious redox behavior in the potential range of 0-0.8V, indicating that the supercapacitor exhibits an activated carbon double-layer energy storage mechanism in this potential range. In the range of 0.8-1.6V, the redox process of poly(9-hydroxyfluorene) / NiO produces a redox peak. Over the entire scan rate range, all cyclic voltammetry curves show the electrochemical redox reaction of the poly(9-hydroxyfluorene) / NiO anode and the charge storage of the double-layer capacitance of the activated carbon cathode. The redox peak current density shows a good linear relationship with the scan rate, and the shape and position of the CV curves are basically consistent without obvious deformation, indicating that the asymmetric supercapacitor has good electrochemical reversibility.

[0050] Among them, the charge and discharge curves of the prepared asymmetric supercapacitor at different current densities are as follows: Figure 7 As shown in the figure, all GCD curves show a clearly symmetrical charge and discharge process, indicating that the asymmetric supercapacitor has reversible charge storage characteristics. According to the GCD curve, it can be calculated that at current densities of 1, 2, 3, 4 and 5 A g -1 When the specific capacitance values of the asymmetric supercapacitor are 245.6, 218.7, 203.1, 167.5 and 155.6 F g, respectively. -1The energy density and power density of the device can be calculated from the specific capacitance of the asymmetric supercapacitor. When the power density is 806.3 Wkg -1 The peak energy density reaches 87.3 Wh kg -1 , and when the power density is 4425.6 W kg -1 The peak energy density remains at 55.3 Wh kg -1 , indicating that the supercapacitor constructed based on the nanoflower-like poly (9-hydroxyfluorene) / NiO composite material exhibits good energy storage performance. The above-prepared asymmetric supercapacitor was subjected to a long-term constant current charge and discharge experiment to test its stability. The relationship between the specific capacitance value and the percentage of initial capacity retained after 5000 charge and discharge cycles is shown in the figure below. Figure 8 As shown in the figure, it can be seen that the specific capacitance after 5000 charge and discharge cycles is still as high as 193.3 F g -1 , it can still maintain 78.7% of the initial specific capacitance value, and the specific capacitance loss is small, indicating that the supercapacitor constructed based on poly (9-hydroxyfluorene) / NiO electrode material has good charge and discharge stability.

[0051] Example 2

[0052] The preparation method of the nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material comprises the following steps:

[0053] (1) Preparation of NiO powder: First, 0.15g nickel sulfate (NiSO4·5H2O), 0.04g acrylamide (C3H5NO surfactant), 0.25g hexamethylenetetramine (C6H 12 N4) were dissolved in 25 mL of deionized water at room temperature, and then the obtained acrylamide solution and hexamethylenetetramine solution were added to the nickel sulfate solution in sequence and mixed evenly with a magnetic stirrer. The mixed solution was transferred to a reactor and hydrothermally reacted at 190 ° C for 4 hours. The reactor was taken out and cooled to room temperature and centrifuged. The obtained precipitate was washed three times with deionized water and anhydrous ethanol respectively, and dried in an oven at 90 ° C for 4 hours to obtain Ni(OH)2. Finally, it was annealed at 400 ° C in a muffle furnace to obtain NiO powder.

[0054] (2) After dissolving 60 mg of NiO powder in 1.5 mL of water, the mixture was dispersed evenly by ultrasonication. 120 μL of the mixture was applied to the FTO electrode and dried at 220 °C for 1.5 h to obtain a NiO electrode.

[0055] (3) 9-hydroxyfluorene and Bu4NBF4 were added to ACN so that the concentration of 9-hydroxyfluorene in acetonitrile was 1.5 mol / L and the concentration of Bu4NBF4 in ACN was 0.2 mol / L. TFA was then added so that the volume of ACN accounted for 20% to obtain an electrolyte.

[0056] (4) Electrochemical polymerization was carried out by a constant potential method, with the NiO electrode, Pt wire, and Ag / AgCl prepared in step (2) as the working electrode, counter electrode, and reference electrode, respectively. The polymerization potential was 2.2 V vs. Ag / AgCl, and the polymerization time was 12 s, to obtain a nanoflower-like poly(9-hydroxyfluorene) / NiO composite material loaded on the electrode.

[0057] Example 3

[0058] The preparation method of the nano-flower-shaped poly (9-hydroxyfluorene) / NiO composite material comprises the following steps:

[0059] (1) Preparation of NiO powder: First, 0.2g nickel sulfate (NiSO4·5H2O), 0.02g acrylamide (C3H5NO surfactant), 0.15g hexamethylenetetramine (C6H 12 N4) were dissolved in 18 mL of deionized water at room temperature, and then the obtained acrylamide solution and hexamethylenetetramine solution were added to the nickel sulfate solution in sequence and mixed evenly with a magnetic stirrer. The mixed solution was transferred to a reactor and hydrothermally reacted at 160 ° C for 8 h. The reactor was taken out and cooled to room temperature and centrifuged. The obtained precipitate was washed three times with deionized water and anhydrous ethanol, respectively, and dried in an oven at 60 ° C for 7 h to obtain Ni(OH)2. Finally, it was annealed at 250 ° C in a muffle furnace to obtain NiO powder.

[0060] (2) After dissolving 40 mg of NiO powder in 0.8 mL of water, the mixture was dispersed evenly by ultrasonication. 90 μL of the mixture was applied to the FTO electrode and dried at 180 °C for 2.5 h to obtain a NiO electrode.

[0061] (3) 9-hydroxyfluorene and Bu4NBF4 were added to ACN so that the concentration of 9-hydroxyfluorene in acetonitrile was 0.8 mol / L and the concentration of Bu4NBF4 in ACN was 0.08 mol / L. TFA was then added so that TFA accounted for 12% of the volume of ACN to obtain an electrolyte.

[0062] (4) Electrochemical polymerization was performed by a constant potential method, with the NiO electrode, Pt wire, and Ag / AgCl prepared in step (2) as the working electrode, counter electrode, and reference electrode, respectively. The polymerization potential was 1.0 V vs. Ag / AgCl, and the polymerization time was 8 s to obtain a nanoflower-like poly(9-hydroxyfluorene) / NiO composite material loaded on the electrode.

Claims

1. A method for preparing a nanoflower-like poly (9-hydroxyfluorene) / NiO composite material, characterized by: The following steps are involved: First, NiO powder is prepared, then dissolved in water and coated on a FTO electrode, followed by drying to obtain a NiO electrode; then, 9-hydroxyfluorene and tetrabutylammonium boron tetrafluoride are added to acetonitrile, followed by trifluoroacetic acid to obtain an electrolyte; finally, a nanoflower-shaped poly(9-hydroxyfluorene) / NiO composite material loaded on the electrode is obtained by electrochemical polymerization; the electrochemical polymerization is performed using a constant potential method; The specific steps for preparing NiO powder are as follows: first, 0.15-0.2g of nickel sulfate, 0.02-0.04g of acrylamide, and 0.15-0.25g of hexamethylenetetramine are dissolved in 18-25mL of deionized water at room temperature, and then the obtained acrylamide solution and hexamethylenetetramine solution are added to the nickel sulfate solution in sequence. The obtained mixed solution is hydrothermally reacted at 160-190°C for 4-8h, cooled to room temperature, centrifuged, and the obtained precipitate is washed and dried in an oven at 60-90°C for 4-7h to obtain Ni(OH)2. Finally, it is annealed at 250-400°C to obtain NiO powder.

2. The method for preparing the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material according to claim 1, characterized in that: The electrochemical polymerization uses NiO electrode, Pt wire and Ag / AgCl as working electrode, counter electrode and reference electrode respectively.

3. The method for preparing the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material according to claim 1, characterized in that: Then, 40-60 mg of NiO powder was dissolved in 0.8-1.5 mL of water and dispersed by ultrasonic. 90-120 μL of the solution was applied to the FTO electrode and dried at 180-220° C. for 1.5-2.5 h.

4. The method for preparing the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material according to claim 1, characterized in that: 9-hydroxyfluorene and tetrabutylammonium boron tetrafluoride are added to acetonitrile so that the concentration of 9-hydroxyfluorene in acetonitrile is 0.8-1.5 mol / L and the concentration of tetrabutylammonium boron tetrafluoride in acetonitrile is 0.08-0.2 mol / L, and trifluoroacetic acid is added so that the trifluoroacetic acid accounts for 12-20% of the volume of the acetonitrile.

5. The method for preparing the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material according to claim 1, characterized in that: When electrochemical polymerization is performed using a constant potential method, the polymerization potential is 1.0-2.2 V vs. Ag / AgCl, and the polymerization time is 8-12 s.

6. A nanoflower-like poly (9-hydroxyfluorene) / NiO composite material, characterized by The nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material is prepared by the preparation method of any one of claims 1 to 5.

7. Use of the nanoflower-shaped poly(9-hydroxyfluorene) / NiO composite material according to claim 6, characterized in that: The prepared nanoflower-like poly (9-hydroxyfluorene) / NiO composite material was used as the anode material and activated carbon as the cathode material to construct an asymmetric supercapacitor.

8. The use of the nanoflower-shaped poly (9-hydroxyfluorene) / NiO composite material according to claim 7, characterized in that: The mass ratio of the anode material to the cathode material is 1:1.2~1:2.0.

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