阅读说明：本技术 一种BiFeO3纳米颗粒复合TiO2纳米管阵列的制备方法 (BiFeO3Nanoparticle composite TiO2Method for preparing nanotube array ) 是由 肖仁政 汪俊 向鹏 韩岳松 王若琪 高振军 洪锋 胡涛 于 2021-07-06 设计创作，主要内容包括：本发明公开了一种BiFeO-(3)纳米颗粒复合TiO-(2)纳米管阵列的制备方法。所涉及的制备方法如下：预处理的钛片与Pt片浸于电解液中,分别连上电源的正极和负极,在施加电压条件下进行阳极氧化反应,反应结束后,将电极用无水乙醇清洗,自然干燥；在500-600°C退火1-2 h,将硝酸铋、硝酸铁和柠檬酸溶于溶剂中,搅拌得到BiFeO-(3)前驱体；TiO-(2)纳米管阵列电极垂直浸入步骤(5)配置的BiFeO-(3)前驱体中,真空浸渍5-30 min；在500-600℃下退火1-2 h,制得BiFeO-(3)纳米颗粒附着的TiO-(2)纳米管阵列。本发明的BiFeO-(3)纳米颗粒附着的TiO-(2)纳米管阵列的比电容强度相较于TiO-(2)纳米管阵列(比电容值：380.1 F/g)提升了21.4%。(The invention discloses BiFeO 3 Nanoparticle composite TiO 2 A method for preparing a nanotube array. The preparation method comprises the following steps: immersing the pretreated titanium sheet and the Pt sheet in electrolyte, respectively connecting with a positive electrode and a negative electrode of a power supply, carrying out anodic oxidation reaction under the condition of applying voltage, cleaning the electrodes by absolute ethyl alcohol after the reaction is finished, and naturally drying; annealing at 500-Dissolving in solvent, stirring to obtain BiFeO 3 A precursor; TiO 2 2 Vertically immersing the nanotube array electrode into the BiFeO prepared in the step (5) 3 Vacuum soaking the precursor for 5-30 min; annealing at 500-600 ℃ for 1-2h to prepare BiFeO 3 Nanoparticle attached TiO 2 An array of nanotubes. BiFeO of the invention 3 Nanoparticle attached TiO 2 Specific capacitance strength of nanotube arrays compared to TiO 2 The nanotube array (specific capacitance value: 380.1F/g) is improved by 21.4%.)

1. BiFeO₃Nanoparticle composite TiO₂The preparation method of the nanotube array is characterized by comprising the following steps:

(1) pretreatment of the titanium sheet: polishing a titanium sheet by using sand paper until the titanium sheet is uniform and bright, performing ultrasonic treatment in deionized water, etching in mixed acid, sequentially soaking in acetone, absolute ethyl alcohol and deionized water, performing ultrasonic cleaning, and air-drying for later use;

(2) preparing electrolyte: reacting NH₄F, placing the mixture in a mixed solution of deionized water and ethylene glycol, and uniformly stirring to obtain an electrolyte;

(3) anodic oxidation: soaking the titanium sheet and the Pt sheet pretreated in the step (1) in the electrolyte in the step (2), respectively connecting a positive electrode and a negative electrode of a power supply, carrying out anodic oxidation reaction under the condition of applying voltage, cleaning the electrodes by absolute ethyl alcohol after the reaction is finished, and naturally drying;

(4) drying and annealing: placing the titanium sheet anodized in the step (3) in a tubular annealing furnace, annealing at 500-600 ℃ for 1-2h, and naturally cooling to room temperature to obtain TiO₂A nanotube array electrode;

(5) configuration of BiFeO₃Precursor: dissolving bismuth nitrate, ferric nitrate and citric acid in a solvent, and stirring to obtain BiFeO₃A precursor;

(6) vacuum impregnation: adding TiO in the step (4)₂Nanotube array electrodeVertically immersing BiFeO prepared in the step (5)₃Vacuum soaking the precursor for 5-30 min;

(7) drying and annealing: preparing the BiFeO-containing material prepared in the step (6)₃TiO of precursor₂Annealing the nanotube array at 500-600 ℃ for 1-2h to prepare BiFeO₃Nanoparticle attached TiO₂An array of nanotubes.

2. BiFeO according to claim 1₃Nanoparticle composite TiO₂The preparation method of the nanotube array is characterized in that the mixed acid is HF and HNO₃、H₂And mixing the O with the volume ratio of 1:4-5:5-6 to obtain a mixed acid solution.

3. BiFeO according to claim 1₃Nanoparticle composite TiO₂The preparation method of the nanotube array is characterized in that NH is contained in the electrolyte₄The mass concentration of F is 0.3-1.0 wt%, and the mass ratio of deionized water to ethylene glycol is 1: 15-20.

4. BiFeO according to claim 1₃Nanoparticle composite TiO₂The preparation method of the nanotube array is characterized in that the anode is oxidized into alternating voltage for oxidation, and the step E is under the constant temperature condition of 30 DEG C_on=40-50 V，t_on=150-200 s，E_off=0 V，t_offAnd (5) changing pressure for 25-40 min alternately for 20-40 s.

5. BiFeO according to claim 4₃Nanoparticle composite TiO₂The preparation method of the nanotube array is characterized in that an alternating voltage E_on=45 V，t_on=180 s，E_off=0 V，t_off=30 s, alternating the pressure swing for 30 min.

6. BiFeO according to claim 1₃Nanoparticle composite TiO₂The preparation method of the nanotube array is characterized in that the bismuth nitrate, the ferric nitrate and the citric acid (chelating agent) are concentratedThe degree is 0.1-0.3 mol/L, and the solvent is one or more of ethanol, glycol or glycol methyl ether.

7. BiFeO according to claim 1₃Nanoparticle composite TiO₂The preparation method of the nanotube array is characterized in that the vacuum impregnation time in the step (6) is 5-30 min.

8. BiFeO according to claim 1₃Nanoparticle composite TiO₂The preparation method of the nanotube array is characterized in that the vacuum degree in the step (6) is less than 0.1 MPa.

9. BiFeO according to claim 8₃Nanoparticle composite TiO₂The preparation method of the nanotube array is characterized in that the vacuum degree in the step (6) is 1 multiplied by 10^-4- 0.05MPa。

10. BiFeO according to claim 1₃Nanoparticle composite TiO₂The preparation method of the nanotube array is characterized in that the heating and drying temperature in the step (7) is 150-.

Technical Field

The invention relates to a super capacitor preparation technology in the field of electrochemical energy storage, in particular to BiFeO₃Nanoparticle composite TiO₂A preparation method of a nanotube array electrode material.

Background

The super capacitor is an electrochemical capacitor, is a novel energy storage device, has the advantages of high specific power, short charging time, high discharging efficiency, long cycle service life, no environmental pollution and the like, and makes up the defects of low power density, slow charging and discharging, safety, damage caused by over-charging and discharging, low capacity of the traditional capacitor and the like of a secondary battery. To a certain extent, the power driving problem of the standby power supply and the new energy automobile is solved. The annual demand has increased since the commercialization of supercapacitors. The super capacitor is widely applied to the fields of new energy automobiles, wind power generation, electronic equipment, national defense and the like as a novel energy storage device. Because the charging and discharging work of the super capacitor is mainly completed by the electrode, the preparation of the electrode with good capacitance characteristic is the premise of constructing the high-performance super capacitor. Electrode materials currently being widely studied are roughly classified into three types, which are carbon materials, metal oxide materials, and conductive polymers, respectively. The metal oxide has good conductivity, and the reversible redox reaction can be simultaneously carried out on the surface and in the electrode, so that the space utilization rate of the whole electrode is improved, and the energy density and the capacitance characteristic of the electrode are obviously enhanced. Due to these unique properties of metal oxidesThe pseudocapacitance characteristics of the super-carbon material are far away from the electric double layer capacitance generated by the super-carbon material in performance, and the difference is usually one to two orders of magnitude, BiFeO₃The composite material has good ferroelectricity and ferromagnetism and has good application in the field of super capacitors.

TiO₂The crystal structure of (a) has three main existing forms in nature: anatase, rutile and brookite (of which anatase and rutile type structures are the most widely studied nano TiO)₂Has the characteristics of high chemical stability, strong catalytic activity, high photoelectric conversion efficiency, low cost, no toxicity and the like, and arouses the interest of scientific researchers at home and abroad. Anodic oxidation of TiO₂The nanotube has the advantages of simple preparation method, controllable aperture and length, good charge separation and transfer characteristics and the like; it is widely used in various fields because of its semiconductor properties and abundance in nature. And nanotube structures generally provide a larger surface area while using less electrode material, resulting in a large increase in mass to capacitance. TiO 2₂The nanotube shows good double-layer capacitance as an electrode material, and has good application prospect in the field of super capacitors.

Disclosure of Invention

The invention aims to provide BiFeO for the situation₃Nanoparticle composite TiO₂A preparation method of a nanotube array electrode material.

The technical scheme of the invention is as follows: BiFeO₃Nanoparticle composite TiO₂The preparation method of the nanotube array electrode material comprises the following steps:

(1) pretreatment of the titanium sheet: polishing a titanium sheet by using sand paper until the titanium sheet is uniform and bright, performing ultrasonic treatment in deionized water, etching in mixed acid, sequentially soaking in acetone, absolute ethyl alcohol and deionized water, performing ultrasonic cleaning, and air-drying for later use; the mixed acid is HF and HNO₃、H₂And mixing the O with the volume ratio of 1:4-5:5-6 to obtain a mixed acid solution.

(2) Preparing electrolyte: reacting NH₄F, placing the mixture in a mixed solution of deionized water and ethylene glycol, and uniformly stirring to obtain an electrolyte; said electrolysisIn liquid, NH₄The mass concentration of F is 0.3-1.5 wt%, and the mass ratio of deionized water to ethylene glycol is 1: 15-20.

(3) Anodic oxidation: soaking the titanium sheet and the Pt sheet pretreated in the step (1) in the electrolyte in the step (2), respectively connecting a positive electrode and a negative electrode of a power supply, carrying out anodic oxidation reaction under the condition of applying voltage, cleaning the electrodes by absolute ethyl alcohol after the reaction is finished, and naturally drying;

the anode is oxidized by alternating voltage, and the step is that under the constant temperature condition of 30 ℃, E_on=40-50 V，t_on=150-200 s，E_off=0 V，t_offAnd (5) changing pressure for 25-40 min alternately for 20-40 s.

Preferably, the alternating voltage E_on=45 V，t_on=180 s，E_off=0 V，t_off=30 s, alternating pressure swing lasts for 30min, and TiO with excellent appearance is obtained₂Nanotube arrays, TiO₂The diameter of the pipe orifice of the nanotube is about 80nm, and the length of the pipe is about 3 mu m. Alternating voltage anodic oxidation of TiO compared with fixed voltage and pulse voltage₂The nanotube array has the advantages of better structural control, more uniform appearance, more uniform distribution, cleaner and tidier surface and more round and more complete pipe orifice. At low voltage, the nanotubes are short and have small tube diameters; under high voltage, the nanotube is longer and the tube diameter is larger, but the voltage TiO is further increased₂The nanotubes will gradually collapse.

(4) Drying and annealing: placing the titanium sheet anodized in the step (4) in a tubular annealing furnace, annealing at 500-600 ℃ for 1-2h, and naturally cooling to room temperature to obtain TiO₂A nanotube array electrode;

(5) configuration of BiFeO₃Precursor: dissolving bismuth nitrate, ferric nitrate and citric acid (chelating agent) in a solvent, wherein the solvent is one or a mixture of ethanol, glycol or ethylene glycol monomethyl ether, and stirring to obtain BiFeO₃A precursor; the concentrations of bismuth nitrate, ferric nitrate and citric acid are 0.1-0.3 mol/L, preferably 0.1 mol/L, respectively. BiFeO when the solution concentration increases to 0.3 mol/L₃Is easy to be attached on TiO₂The surface of the aligned nanotube presents a thin filmStructure and easy production of Bi₂Fe₄O₉And the like. When the solution concentration is low, such as 0.05 mol/L, longer reaction time is needed, and BiFeO₃The crystal nuclei do not easily agglomerate into particles.

(6) Vacuum impregnation: adding TiO in the step (4)₂Vertically immersing the nanotube array electrode into the BiFeO prepared in the step (5)₃Vacuum soaking in the precursor for 10-30 min at vacuum degree of below 0.1 MPa, preferably at vacuum degree of 1 × 10^-4-0.05 MPa; based on the principle of saving resources and cost, as a preferred scheme, the vacuum impregnation time is 10 min, and the vacuum degree is 0.05 MPa. The vacuum impregnation can well remove gas in the nanotube, is beneficial to the metal ions to be impregnated to enter the pore canal, and has more uniform distribution of the metal ions. Ultrasonic impregnation can damage the structure of the nanotubes to a certain extent and even cause the breakage of the nanotubes; the hydrothermal method is complicated in operation and easy to generate iron-bismuth oxide miscellaneous items.

(7) Drying and annealing: preparing the BiFeO-containing material prepared in the step (6)₃TiO of precursor₂Annealing the nanotube array at 500-600 ℃ for 1-2h to prepare BiFeO₃Nanoparticle attached TiO₂A nanotube array electrode. At 0.5 mol/L of Na₂SO₄The capacitance test was carried out in solution at a current density of 1A/g. The capacitance characteristic test shows that BiFeO₃Nanoparticle attached TiO₂Specific capacitance strength of nanotube arrays compared to TiO₂The nanotube array (specific capacitance: 380.1F/g) is improved by 21.4 percent and can reach 461.5F/g and above.

Drawings

FIG. 1 shows TiO prepared by anodic oxidation in example 1₂The field emission Scanning Electron Microscope (SEM) of the surface of the nanotube array material has the magnification of 10 ten thousand times and TiO at the upper right corner₂Field emission Scanning Electron Microscopy (SEM) of nanotube array material cross-section.

FIG. 2 shows TiO prepared by anodic oxidation in example 1₂X-ray diffraction pattern (XRD) of nanotube array material.

FIG. 3 is BiFeO prepared in example 7 under a vacuum of 0.05MPa₃Nanoparticle composite TiO₂The field emission scanning electron microscope image of the nanotube array surface is 5 ten thousand times of magnification.

FIG. 4 is BiFeO prepared in example 7₃Nanoparticle composite TiO₂X-ray diffraction patterns (XRD) of nanotube array electrode materials. Wherein the abscissa is twice the diffraction angle (2 θ) and the ordinate is the diffraction peak intensity (a.u.).

FIG. 5 is BiFeO prepared without citric acid in example 6₃Nanoparticle composite TiO₂X-ray diffraction patterns (XRD) of the nanotube array electrode material. Wherein the abscissa is twice the diffraction angle (2 θ) and the ordinate is the diffraction peak intensity (a.u.).

FIG. 6 is BiFeO prepared in example 9 under a vacuum of 0.1 MPa₃Nanoparticle composite TiO₂The field emission scanning electron microscope image of the nanotube array surface is 2 ten thousand times of magnification.

Detailed Description

Example 1BiFeO₃Nanoparticle composite TiO₂The preparation method of the nanotube array electrode material comprises the following steps:

(1) pretreatment of the titanium sheet: grinding a metal pure titanium sheet with the size specification of 10 multiplied by 15 mm by 1000#, 1500# and 2000# abrasive paper to be uniform and bright, performing 50W ultrasonic treatment in deionized water for 3 min, and then using HF/HNO₃/H₂Etching with mixed acid with O volume ratio of 1:4:5 for 1min, and repeating the etching twice;

(2) ultrasonic cleaning: and (2) immersing the titanium sheet obtained in the step (1) in acetone, absolute ethyl alcohol and deionized water in sequence, and carrying out ultrasonic treatment for 3 min with the power of 50W, and repeating the steps twice. Air-drying for later use;

(3) preparing electrolyte: 0.5 wt% NH₄F, placing the mixture in a mixed solution of 5wt% of deionized water and 95 wt% of ethylene glycol, and uniformly stirring to obtain an electrolyte;

(4) anodic oxidation: soaking the titanium sheet and the Pt sheet in the step (2) in the electrolyte in the step (3), respectively connecting a positive electrode and a negative electrode of a power supply, and circularly applying the potential for E and the time_on=45 V，t_on=180 s，E_off=0 V，t_off=30 s, at constant temperature of 30 ℃, for 3And 0 min. After the reaction is finished, cleaning the electrode by using absolute ethyl alcohol, and naturally drying;

(5) drying and annealing: and (5) annealing the titanium sheet in the step (4) in a tubular annealing furnace at the annealing temperature of 500 ℃ for 1 h. Naturally cooling to room temperature to obtain TiO₂The SEM and XRD of the nanotube array are shown in figures 1 and 2; the specific capacitance strength was 380.1F/g. As can be seen from the attached FIG. 1 of the present invention, TiO₂The arrangement of the nanotubes is tidy, the pipe diameter is kept between 80 and 85nm, and the section diagram of the nanotubes is shown at the upper right corner, which shows that the length of the nanotubes is about 2.76 mu m.

(6) Configuration of BiFeO₃Precursor: dissolving 0.10mol/L bismuth nitrate, 0.10mol/L ferric nitrate and 0.10mol/L citric acid (chelating agent) in ethylene glycol solution, and stirring at 60 ℃ to obtain BiFeO₃A precursor;

(7) vacuum impregnation: adding TiO in the step (5)₂Vertically immersing the nanotube array electrode into the BiFeO prepared in the step (6)₃Putting the precursor in a vacuum environment of 0.08 MPa for 10 min;

(8) drying and annealing: preparing the BiFeO-containing material prepared in the step (7)₃TiO of precursor₂Annealing the nanotube array electrode for 1h at 500 ℃ to prepare BiFeO₃Nanoparticle attached TiO₂The SEM and XRD of the nanotube array electrode are shown in FIGS. 3 and 4. The apparent anatase form of TiO can be seen from FIG. 2₂And no hetero-phase. As can be seen from FIG. 3, TiO₂The surface of the nanotube has particles attached. From FIG. 4, it is apparent that the Ti substrate and anatase TiO form₂Diffraction peak of (1), wherein BiFeO₃The diffraction peak of (A) is relatively clear because of BiFeO₃The number of the particles is large, and a certain amount of BiFeO₃The particles are deposited on the nanotube walls or bottom.

Capacitance test (as per the following references): using CHI660E electrochemical workstation and three-electrode reaction container, and adopting three-electrode method, Pt sheet as counter electrode and Ag/AgCl electrode as reference electrode. At 0.5 mol/L of Na₂SO₄The capacitance test was carried out in solution at a current density of 1A/g. The capacitance characteristic test shows that BiFeO₃Nanoparticle attached TiO₂The specific capacitance strength of the nanotube array was 461.5F/g.

Reference documents: the preparation of the mesoporous nickel oxide film and the performance research of the super capacitor [ J ], the material report B, the research article 2014, 28: 32-34.

Example 2

0.5 wt% NH₄F is placed in 5wt% H₂And O, and a 95 wt% glycol mixed solution, and stirring uniformly. Then the electrolyte is obtained. The amounts of other raw materials and the procedure were the same as in example 1, and the obtained TiO was₂The SEM and XRD patterns of the nanotube array sample are similar to those of FIGS. 1 and 2, with almost no change in the length of the nanotube, the diameter of the tube being about 90-100 nm, and the specific capacitance being 376.3F/g.

Example 3

Potential and time of cyclic application of E_on=50 V，t_on =180 s，E_off =0 V，t_offAnd (6) keeping the temperature of 30 ℃ for 30min for =30 s. The amounts of other raw materials and the procedure were the same as in example 1, and the obtained TiO was₂The SEM image and XRD image of the nanotube array sample are similar to those of the images 1 and 2, but the length of the nanotube tube is about 2.7-3.1 mu m, the tube diameters are basically the same, and the specific capacitance is 379.1F/g.

Example 4

Potential and time of cyclic application of E_on=45 V，t_on =200 s，E_off =0 V，t_offAnd (6) keeping the temperature of 30 ℃ for 30min for =30 s. The amounts of other raw materials and the procedure were the same as in example 1, and the obtained TiO was₂The SEM image and XRD image of the nanotube array sample are similar to those of the images 1 and 2, the tube length of the nanotubes is increased to about 2.8-3.3 mu m, the tube diameters are basically the same, and the specific capacitance is 375.5F/g.

Example 5

Potential and time of cyclic application of E_on=45 V，t_on =180 s，E_off =0 V，t_offAnd the temperature is kept constant at 30 ℃ for 30min by =25 s. The amounts of other raw materials and the procedure were the same as in example 1, and the obtained TiO was₂The SEM image and XRD image of the nanotube array sample are similar to those of the images 1 and 2, the length of the nanotubes is about 2.7-3.1 mu m, the tube diameters are basically the same, and the specific electricity isThe capacity was 364.2F/g.

Example 6

Configuration of BiFeO₃Citric acid (chelating agent) is not added in the precursor. The procedure of the other raw materials was the same as that of example 1, and BiFeO was obtained₃Nanoparticle attached TiO₂The SEM of the nanotube array electrode sample is similar to that of figure 3, the XRD is shown in figure 5, and the test result of the XRD shows that the sample has more Bi₂O₃、Bi₂Fe₄O₉Equal impurity phase, unsatisfactory capacitance test and 419.8F/g specific capacitance.

Example 7

Configuration of BiFeO₃Ethylene glycol methyl ether is used as a solvent. The operation steps are the same as those of the example 1 except for the other raw material dosage, the SEM picture and the XRD picture of the obtained sample are similar to those of the picture 3 and the picture 4, the tube length is about 2.5-2.8 mu m, the tube diameter is about 60-80nm, and the BiFeO is₃The particle size is 50-70 nm, and the specific capacitance is 455.7F/g.

Example 8

Configuration of BiFeO₃Pure water is used as the solvent. Other raw material amounts and operation procedures were the same as those in example 1, and no sample could be obtained.

Example 9

Adding TiO in the step (5)₂Vertically immersing the nanotube array electrode into the BiFeO prepared in the step (6)₃And putting the precursor in a vacuum environment for 10 min. The vacuum degree was 0.1 MPa, the other raw materials were used, the operation was the same as in example 1, the SEM of the sample was as shown in FIG. 6, and BiFeO₃Is attached to TiO in a film form₂The surface of the nanotubes. XRD pattern is similar to that of FIG. 4, BiFeO₃The particles were of substantially the same size and had a specific capacitance of 459.0F/g.

Example 10

Adding TiO in the step (5)₂Vertically immersing the nanotube array electrode into the BiFeO prepared in the step (6)₃And putting the precursor in a vacuum environment for 10 min. Degree of vacuum 1X 10^-2MPa, other raw materials, operating procedure the same as in example 1, SEM and XRD patterns of the obtained samples similar to those of FIGS. 3 and 4, BiFeO₃The particles were of substantially the same size and had a specific capacitance of 461.7F/g.

Example 11

Adding TiO in the step (5)₂Vertically immersing the nanotube array electrode into the BiFeO prepared in the step (6)₃And putting the precursor in a vacuum environment for 10 min. Degree of vacuum 1X 10^-3MPa, other raw materials, operating procedure the same as in example 1, SEM and XRD patterns of the obtained samples similar to those of FIGS. 3 and 4, BiFeO₃The particles were of substantially the same size and had a specific capacitance of 462.4F/g.

Example 12

Adding TiO in the step (5)₂Vertically immersing the nanotube array electrode into the BiFeO prepared in the step (6)₃And putting the precursor in a vacuum environment for 10 min. Degree of vacuum 1X 10^-4MPa, other raw materials, operating procedure the same as in example 1, SEM and XRD patterns of the obtained samples similar to those of FIGS. 3 and 4, BiFeO₃The particles were substantially the same size, 463.1F/g.

Example 13

Adding TiO in the step (5)₂Vertically immersing the nanotube array electrode into the BiFeO prepared in the step (6)₃Putting the precursor in a vacuum environment with the vacuum degree of 0.05MPa for 3 min, using other raw materials, operating the steps the same as example 1, and adopting SEM pictures and XRD pictures similar to those of figures 1 and 2, which means that BiFeO is obtained under the condition of short vacuum impregnation time₃Particles could not be formed and the specific capacitance intensity was 376.3F/g.

Example 14

Adding TiO in the step (5)₂Vertically immersing the nanotube array electrode into the BiFeO prepared in the step (6)₃Placing the precursor in a vacuum environment with the vacuum degree of 0.05MPa for 15 min, using other raw materials, and performing the same operation steps as example 1, wherein the SEM graph and XRD graph of the obtained sample are similar to those of figures 3 and 4, and BiFeO₃The particles were of substantially the same size and had a specific capacitance strength of 459.4F/g.

Example 15

Adding TiO in the step (5)₂Vertically immersing the nanotube array electrode into the BiFeO prepared in the step (6)₃Placing the precursor in a vacuum environment with a vacuum degree of 0.05MPa for 20 minThe amounts of raw materials and the procedure were the same as in example 1, and the SEM and XRD patterns of the obtained samples were similar to those of FIGS. 3 and 4, BiFeO₃The particles were of substantially the same size and had a specific capacitance strength of 462.4F/g.

Example 16

Adding TiO in the step (5)₂Vertically immersing the nanotube array electrode into the BiFeO prepared in the step (6)₃Placing the precursor in a vacuum environment with the vacuum degree of 0.05MPa for 30min, using other raw materials, and performing the same operation steps as example 1, wherein the SEM graph and XRD graph of the obtained sample are similar to those of figures 3 and 4, and BiFeO₃The particles were of substantially the same size and had a specific capacitance strength of 460.7F/g.