Preparation method of Bi2O3 rod-like material rich in oxygen vacancies as well as preparation method and application of Bi2O3 rod-like material rich in oxygen vacancies

Abstract

The invention provides a Bi2O3 rod-like material rich in oxygen vacancies and a preparation method of the Bi2O3 rod-like material rich in oxygen vacancies. The invention provides a Bi2O3 rod-like material rich in oxygen vacancies and a preparation method thereof, and the preparation method comprises the following steps: firstly, uniformly mixing bismuth salt, trimesic acid, methanol and N, N-dimethylformamide, and carrying out a hydrothermal reaction to obtain a Bi-MOF rod-like precursor; then adding the Bi-MOF into a potassium hydroxide solution, and reacting to obtain Bi2O3; finally, Bi2O3 is reduced in the atmosphere of hydrogen-argon mixed gas, and the Bi2O3 rod-like material rich in oxygen vacancies is obtained. The MOF is utilized to derive the porous micro-nano structure and introduce oxygen vacancies, so that the number of active sites, the conductivity and the stability of the material are increased, and the performance of the supercapacitor is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of supercapacitor electrode materials, and particularly relates to a method for preparing a Bi2O3 rod-shaped material rich in oxygen vacancies. Background Art

[0002] Supercapacitors have attracted extensive attention due to their high power, fast charging, and extremely long cycle life. The electrode materials of supercapacitors should have high conductivity, high charge storage surface area, and high electrochemical stability. The synthesis of transition metal oxide electrode materials with high specific capacity and stability through simple, safe, and economical methods is a current research hotspot.

[0003] Among metal oxides, bismuth oxide (Bi2O3), as a typical negative electrode material, has attracted widespread attention in the field of energy storage due to its advantages such as low price, environmental friendliness, simple preparation, and high theoretical specific capacity. However, due to the poor conductivity and unstable structure of Bi2O3 itself, the actual capacity is far lower than the theoretical specific capacity, which can no longer meet the current practical applications. In recent years, studies have pointed out that on the one hand, the utilization rate of Bi2O3 can be improved by constructing a unique micro-nano structure; on the other hand, defect engineering can change the electronic and lattice structure of the electrode material to improve the conductivity and the number of active sites. The present invention utilizes oxygen vacancies to increase the active sites and conductivity of the material; and utilizes MOF-derived porous micro-nano structures to increase the specific surface area and structural stability, thereby improving the capacity, rate performance and cycle stability of the supercapacitor. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a Bi2O3 rod-shaped material rich in oxygen vacancies. The Bi2O3 rod-shaped material rich in oxygen vacancies obtained by the method has the advantage of significantly improving the electrochemical performance.

[0005] The technical solution of the present invention is: a method for preparing Bi2O3 rods rich in oxygen vacancies, characterized by comprising the following steps:

[0006] (1) Dissolving bismuth nitrate pentahydrate and trimesic acid in a mixed solvent of methanol and N,N-dimethylformamide (DMF), stirring at room temperature for 30 minutes to form a uniform reaction solution; then reacting for a period of time, cooling to room temperature, washing with anhydrous ethanol, centrifuging the product three times, and drying at 60°C for 12 hours to obtain a Bi-MOF rod-shaped precursor;

[0007] (2) 0.15 g of Bi-MOF precursor was added to a potassium hydroxide solution, reacted at room temperature for a period of time, and then the product was washed alternately with anhydrous ethanol and deionized water for 6 times, centrifuged and dried at 60 ° C for 12 h to obtain Bi2O3 rod-shaped material;

[0008] (3) The Bi2O3 obtained in step (2) is reduced in a hydrogen-argon mixed gas atmosphere for a period of time to obtain a Bi2O3 rod-shaped material rich in oxygen vacancies, referred to as Vo-Bi2O3.

[0009] In the step (1), the amount of bismuth nitrate pentahydrate is preferably 0.05 to 0.25 g, and the amount of trimesic acid is preferably 0.25 to 1.5 g.

[0010] In the step (1), the total volume of the mixed solvent is preferably 60 mL, and the volume ratio of methanol to DMF is preferably 1:(2-5), but the optimal volume ratio is 1:4.

[0011] In the step (1), the reaction temperature is preferably 90 to 150° C., and the reaction time is preferably 12 to 48 hours.

[0012] In the step (2), the concentration of potassium hydroxide is preferably 0.5 to 3 mol / L, and the volume of potassium hydroxide is preferably 20 to 60 mL.

[0013] In the step (2), the reaction time is preferably 1.5 to 3 hours.

[0014] In the step (3), the volume concentration of hydrogen in the hydrogen-argon mixed gas is 5%.

[0015] In the step (3), the reduction reaction temperature is optimized to 200-350° C., and the reaction time is optimized to 0.5-2 hours.

[0016] In summary, the Bi2O3 rod-shaped material rich in oxygen vacancies of the present invention has the following beneficial effects:

[0017] (1) The cost of raw materials required to prepare Vo-Bi2O3 is low, the synthesis process is simple, and the Vo-Bi2O3 material itself has good conductivity, rich redox reactions, and strong electrochemical activity. Compared with Bi2O3, Vo-Bi2O3 contains more redox reaction sites, shortens the path of ion diffusion, increases conductivity, and improves electrochemical reaction activity. Bi-MOF is converted into Bi2O3 by room temperature hydrolysis, and then reduced under hydrogen-argon mixed gas to obtain Vo-Bi2O3, which largely retains the advantages of MOF materials such as porous morphology and multiple active sites, while improving the material's specific capacitance and cycle stability. Therefore, the material is improved in many aspects such as specific capacitance and rate performance.

[0018] (2) The oxygen vacancy-rich Bi2O3 nanorod material prepared by the present invention exhibits high specific capacitance and rate performance in electrochemical tests. At a current density of 1A / g, the electrode material has a high specific capacitance of 950F / g. At a current density of 10A / g, the electrode material also has a specific capacitance of 528F / g, and a rate performance of 55.6%.

[0019] (3) The preparation method of the present invention is simple and effective, and the construction of the nanorod-shaped electrode material demonstrated can be simply extended to construct other defect-rich transition metal compound micro-nanostructures for electrochemical energy storage devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a scanning electron microscope image of the Bi-MOF prepared in step (1) of Example 1 of the present invention;

[0021] Figure 2 is a scanning electron microscope image of Bi2O3 prepared in step (2) of Example 1 of the present invention;

[0022] Figure 3 is a scanning electron microscope image of Vo-Bi2O3 prepared in step (3) of Example 1 of the present invention;

[0023] Figure 4 is the X-ray diffraction pattern of Bi2O3 prepared in step (2) and Vo-Bi2O3 prepared in step (3) in Example 1 of the present invention;

[0024] Figure 5 The cyclic voltammetry curves of Vo-Bi2O3 prepared in step (3) of Example 1 of the present invention as an electrode material at different scan rates in a 6M KOH electrolyte solution;

[0025] Figure 6 is a constant current discharge curve diagram of Vo-Bi2O3 prepared in step (3) of Example 1 of the present invention as an electrode material at different current densities in a 6M KOH electrolyte solution;

[0026] Figure 7 It is the specific capacitance of Bi2O3 prepared in step (2) and Vo-Bi2O3 prepared in step (3) in Example 1 of the present invention as electrode materials in 6M KOH electrolyte solution. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present invention are described in further detail below with reference to the accompanying drawings and examples.

[0028] Embodiment 1:

[0029] (1) 0.15 g of bismuth nitrate pentahydrate and 0.75 g of trimesic acid were dissolved in a mixed solvent of 12 mL of methanol and 48 mL of DMF, and stirred at room temperature for 30 min to form a uniform reaction solution; then the mixture was reacted at 120° C. for 24 h, cooled to room temperature, washed with anhydrous ethanol, centrifuged the product three times, and dried at 60° C. for 12 h to obtain a Bi-MOF rod-shaped precursor; the scanning electron microscopy image of the prepared Bi-MOF is shown in FIG. Figure 1 As shown, it has a rod-like morphology and a smooth surface;

[0030] (2) 0.15 g of Bi-MOF was dispersed in 30 mL of 1 mol / L potassium hydroxide solution and reacted at room temperature for 2 h. The product was washed 6 times with anhydrous ethanol and deionized water alternately, centrifuged and dried at 60 °C for 12 h to obtain Bi2O3 rod-shaped material. The scanning electron microscopy of the prepared Bi2O3 is as follows: Figure 2 As shown, it presents an aggregated rod-like structure;

[0031] (3) The Bi2O3 obtained in step (2) is reduced in a 5% hydrogen-argon mixed gas atmosphere at 250°C for 30 min to obtain a Bi2O3 rod-shaped material rich in oxygen vacancies, referred to as Vo-Bi2O3. The scanning electron microscopy of the prepared Vo-Bi2O3 is as follows: Figure 3 As shown, it presents an aggregated rod-like structure with a rough surface.

[0032] The X-ray diffraction patterns of Bi2O3 and Vo-Bi2O3 prepared according to the above steps are as follows: Figure 4 shown.

[0033] The cyclic voltammetry curves of Vo-Bi2O3 prepared in the above steps as supercapacitor electrode material at different scan rates in 6M KOH electrolyte solution are as follows: Figure 5 As shown; constant current discharge curves at different current densities in 6MKOH electrolyte solution, such as Figure 6 shown.

[0034] The Bi2O3 and Vo-Bi2O3 prepared in the above steps were used as supercapacitor electrode materials, and the specific capacitance was tested at different current densities in a 6M KOH electrolyte solution. Figure 7 As shown in the graph, at a current density of 1 A / g, Bi2O3 and Vo-Bi2O3 have specific capacitances of 405.5 F / g and 950 F / g, respectively, indicating that the oxygen vacancy-rich Vo-Bi2O3 electrode material has higher electrochemical performance.

[0035] Embodiment 2:

[0036] (1) 0.25 g of bismuth nitrate pentahydrate and 0.75 g of trimesic acid were dissolved in a mixed solvent of 12 mL of methanol and 48 mL of DMF, and stirred at room temperature for 30 min to form a uniform reaction solution; then reacted at 120° C. for 24 hours, cooled to room temperature, washed with anhydrous ethanol, centrifuged the product three times, and dried at 60° C. for 12 hours to obtain a Bi-MOF rod precursor;

[0037] (2) 0.15 g of Bi-MOF was dispersed in 30 mL of 1 mol / L potassium hydroxide solution, reacted at room temperature for 2 h, and then the product was washed alternately with anhydrous ethanol and deionized water for 6 times, centrifuged and dried at 60 °C for 12 h to obtain Bi2O3 rod-shaped material;

[0038] (3) The Bi2O3 obtained in step (2) is reduced in an atmosphere of 5% hydrogen-argon mixed gas at 200°C for 30 minutes to obtain a Bi2O3 rod-shaped material rich in oxygen vacancies, referred to as Vo-Bi2O3.

[0039] The Vo-Bi2O3 prepared in the above steps is used as a supercapacitor electrode material, and the specific capacitance at different current densities is tested in a 6M KOH electrolyte solution. The electrode material has a specific capacitance of 670F / g at a current density of 1A / g.

[0040] Embodiment 3:

[0041] (1) 0.15 g of bismuth nitrate pentahydrate and 0.75 g of trimesic acid were dissolved in a mixed solvent of 12 mL of methanol and 48 mL of DMF, and stirred at room temperature for 30 min to form a uniform reaction solution; then reacted at 120° C. for 24 hours, cooled to room temperature, washed with anhydrous ethanol, centrifuged the product three times, and dried at 60° C. for 12 hours to obtain a Bi-MOF rod precursor;

[0042] (2) 0.15 g of Bi-MOF was dispersed in 45 mL of a 1.5 mol / L potassium hydroxide solution, reacted at room temperature for 2 h, and then the product was washed alternately with anhydrous ethanol and deionized water for 6 times, centrifuged, and dried at 60 °C for 12 h to obtain a Bi2O3 rod-shaped material;

[0043] (3) The Bi2O3 obtained in step (2) is reduced in an atmosphere of 5% hydrogen-argon mixed gas at 250°C for 60 minutes to obtain a Bi2O3 rod-shaped material rich in oxygen vacancies, referred to as Vo-Bi2O3.

[0044] The Vo-Bi2O3 prepared in the above steps is used as a supercapacitor electrode material, and the specific capacitance at different current densities is tested in a 6M KOH electrolyte solution. The electrode material has a specific capacitance of 753F / g at a current density of 1A / g.

[0045] Embodiment 4:

[0046] (1) 0.15 g of bismuth nitrate pentahydrate and 0.75 g of trimesic acid were dissolved in a mixed solvent of 12 mL of methanol and 48 mL of DMF, and stirred at room temperature for 30 min to form a uniform reaction solution; then reacted at 150° C. for 12 hours, cooled to room temperature, washed with anhydrous ethanol, centrifuged the product three times, and dried at 60° C. for 12 hours to obtain a Bi-MOF rod precursor;

[0047] (2) 0.15 g of Bi-MOF was dispersed in 30 mL of 1 mol / L potassium hydroxide solution, reacted at room temperature for 2 h, and then the product was washed alternately with anhydrous ethanol and deionized water for 6 times, centrifuged and dried at 60 °C for 12 h to obtain Bi2O3 rod-shaped material;

[0048] (3) The Bi2O3 obtained in step (2) is reduced in an atmosphere of 5% hydrogen-argon mixed gas at 300°C for 60 minutes to obtain a Bi2O3 rod-shaped material rich in oxygen vacancies, referred to as Vo-Bi2O3.

[0049] The Vo-Bi2O3 prepared in the above steps is used as a supercapacitor electrode material, and the specific capacitance at different current densities is tested in a 6M KOH electrolyte solution. The electrode material has a specific capacitance of 598F / g at a current density of 1A / g.

[0050] The embodiments described above are detailed descriptions of the technical solutions of the present invention, which should be understood as specific implementation measures of the present invention and are not used to summarize the present invention. Any modifications, supplements or similar replacements made within the scope of the principles of the present invention shall fall within the scope of protection that the present invention should enjoy.

Claims

1. A method for preparing a Bi2O3 rod-shaped material having rich oxygen vacancies, characterized in that The following steps are involved: (1) 0.15 g of bismuth nitrate pentahydrate and 0.75 g of trimesic acid were dissolved in a mixed solvent of 12 mL of methanol and 48 mL of N,N-dimethylformamide, and stirred at room temperature for 30 min to form a uniform reaction solution; then the mixture was reacted at 120 °C for 24 hours, cooled to room temperature, washed with anhydrous ethanol, centrifuged the product three times, and dried at 60 °C for 12 hours to obtain a Bi-MOF rod precursor; (2) 0.15 g of Bi-MOF was dispersed in 30 mL of 1 mol / L potassium hydroxide solution, reacted at room temperature for 2 h, and then the product was washed alternately with anhydrous ethanol and deionized water for 6 times, centrifuged and dried at 60 °C for 12 h to obtain Bi2O3 rod-shaped material; (3) The Bi2O3 obtained in step (2) is reduced in an atmosphere of 5% hydrogen-argon mixed gas at 250°C for 30 minutes to obtain a Bi2O3 rod-shaped material rich in oxygen vacancies.

2. Use of the Bi2O3 rod-shaped material rich in oxygen vacancies prepared by the preparation method according to claim 1 as a supercapacitor electrode material.

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