A Construction Method of Iron-Cobalt Intermetallic Compounds for Capacitive Deionization

Abstract

The present invention relates to a method for constructing iron-cobalt intermetallic compounds applied to capacitive deionization. The object of the present invention is to solve the problems of easy oxidation and fewer active sites in the synthesis process of existing intermetallic compounds, and to provide a method for constructing iron-cobalt intermetallic compounds with high adsorption performance. Method: Using iron nitrate, cobalt nitrate, polyvinylpyrrolidone and deionized water as raw materials, a method for constructing iron-cobalt intermetallic compounds with high adsorption performance is obtained by using the calcination method and liquid nitrogen quenching method, providing a method for improving the capacitive deionization performance of existing intermetallic compounds.

Description

Technical Field

[0001] The present invention relates to a method for constructing iron-cobalt intermetallic compounds applied to capacitive deionization. Background Art

[0002] As a new desalination method, capacitive deionization technology operates under normal pressure and room temperature conditions. When a voltage is applied, the liquid flows between or through the electrodes, and ions are stored in the electrodes by the action of the electric field force. Subsequently, when a reverse voltage is applied and the electrodes are short-circuited, electrode regeneration can be achieved. It has the advantages of low voltage, simple operation, no secondary pollution, low energy consumption, and easy electrode regeneration. Due to the overdraft of groundwater resources, the salt concentration of groundwater increases or seawater intrusion occurs in coastal areas, resulting in a shortage of fresh water resources. Capacitive deionization technology can convert it into valuable fresh water resources to alleviate the shortage of fresh water resources. Currently, one of the research focuses is to develop high-efficiency and abundant electrode materials.

[0003] Iron-cobalt intermetallic compounds have more excellent electrochemical activity than single-metal iron / cobalt, but the problems of easy oxidation during the synthesis process and few electrochemical active sites need to be improved. During the synthesis of iron-cobalt intermetallic compounds, by adding polyvinylpyrrolidone, the iron-cobalt intermetallic compounds are prevented from being oxidized, and a method of creating defects by quenching with liquid nitrogen is used to provide abundant electrochemical active sites, thereby improving the capacitive deionization performance, which has important research significance for solving the problem of fresh water resource shortage. Summary of the Invention

[0004] The object of the present invention is to overcome the problems of easy oxidation and few reactive sites of iron-cobalt intermetallic compounds, and to provide a simple, novel and high-yield construction method.

[0005] A method for constructing iron-cobalt intermetallic compounds applied to capacitive deionization of the present invention is completed according to the following steps:

[0006] (1) Add polyvinylpyrrolidone to deionized water, and stir well at room temperature to dissolve it to obtain an aqueous polyvinylpyrrolidone solution;

[0007] (2) Add cobalt nitrate and iron nitrate to the aqueous polyvinylpyrrolidone solution in step (1) respectively, stir at room temperature to obtain solution A, and place solution A in an oven to dry for 24 hours;

[0008] (3) Place 0.2 g of the dried product in step (2) in a tubular furnace, calcine it under the protection of N2, and then quench it with liquid nitrogen to obtain an iron-cobalt intermetallic compound material;

[0009] In the step (1), the mass of polyvinylpyrrolidone is 0.2 - 2 g, the volume of deionized water is 10 - 60 ml, and the stirring time is 0.5 - 2 hours;

[0010] In step (2), 0.5 - 2 g of cobalt nitrate and 0.2 - 1 g of iron nitrate are used, the stirring time is 2 - 8 hours, and the drying conditions are 70 - 120 °C for 22 - 28 hours;

[0011] In step (3), the calcination temperature is 600 - 900 °C, the calcination time is 1 - 3 hours, and the liquid nitrogen quenching temperature is 50 - 700 °C.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention constructs an iron - cobalt intermetallic compound with high adsorption performance, which can be prepared in a relatively short time during the construction process. In addition, the synthesis of this material does not require complex equipment, and the prepared material has excellent capacitive deionization performance. Description of the Drawings

[0013] Figure 1 It is the scanning electron microscope image of the iron - cobalt intermetallic compound in Example 1;

[0014] Figure 2 It is the powder X - ray diffraction spectrum of the iron - cobalt intermetallic compound in Example 1 and the control group;

[0015] Figure 3 It is the X - ray photoelectron energy spectrum of the iron - cobalt intermetallic compound in Example 1;

[0016] Figure 4 It is the desalination capacity performance diagram of the iron - cobalt intermetallic compound in Example 1. Detailed Embodiments

[0017] The technical solution of the present invention is not limited to the following specific embodiments. The following specific embodiments are only used to illustrate the present invention and are not limited by the technical solutions described in the embodiments of the present invention. Those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced to achieve the same technical effect. As long as it meets the use requirements, it is within the protection scope of the present invention.

[0018] A method for constructing an iron - cobalt intermetallic compound applied to capacitive deionization in this embodiment is completed according to the following steps:

[0019] (1) At room temperature, 1 g of polyvinylpyrrolidone is added to 30 mL of deionized water and stirred for 1 hour to dissolve it, obtaining an aqueous polyvinylpyrrolidone solution;

[0020] (2) 1.05 g of cobalt nitrate and 0.45 g of iron nitrate are respectively added to the aqueous polyvinylpyrrolidone solution in step (1). At room temperature, it is stirred for 5 hours to obtain solution A. Then, solution A is placed in an oven and dried at 95 °C for 24 hours;

[0021] (3) Place 0.2 g of the dried product from step (2) in a tube furnace, calcine it at 700 °C for 1 hour under N2 protection, then cool it to 100 °C and quench it with liquid nitrogen to obtain the iron-cobalt intermetallic compound material.

[0022] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0023] Figure 1 It is the scanning electron microscope image of the iron-cobalt intermetallic compound in Example 1. The iron-cobalt intermetallic compound is nanoparticles coated with a carbon film. Due to the rapid quenching with liquid nitrogen after the calcination process, cobalt and iron metals are instantaneously cooled to form a solid solution;

[0024] Figure 2 It is the powder X-ray diffraction pattern of the iron-cobalt intermetallic compound in Example 1 and the control group. The diffraction peaks at positions such as 45.2, 65.7, and 83.3° correspond to the (110), (200), and (211) crystal planes (PDF#00-050-0795), indicating that the product is an iron-cobalt intermetallic compound;

[0025] Figure 3 It is the X-ray photoelectron spectroscopy pattern of the iron-cobalt intermetallic compound in Example 1. From the full spectrum of the iron-cobalt intermetallic compound, it can be seen that the diffraction peaks at positions such as 780.0, 284.2, and 711.0 eV correspond to Co 2p, C 1s, and Fe 2p. It shows that the material contains elements such as cobalt, iron, and carbon. From the Co 2p spectrum of the iron-cobalt intermetallic compound, it can be seen that the diffraction peaks at positions such as 780.5, 781.2, 789.8, and 794.8 eV correspond to Co 0 、Co 2+ 、Co 3+ and Co 0 correspond. From the Fe 2p spectrum of the iron-cobalt intermetallic compound, it can be seen that the diffraction peaks at positions such as 709.8, 712.5, 718.5, 723.6, and 726.3 eV correspond to Fe 2+ 、Fe 3+ 、Fe 0 、Fe 2+ and Fe 3+ correspond. The above results indicate that the product is an iron-cobalt intermetallic compound;

[0026] Figure 4 It is the desalination capacity performance diagram of the iron-cobalt intermetallic compound in Example 1. At a voltage of 1.6 V and a sodium chloride concentration of 500 mg / L, the desalination capacity of the iron-cobalt intermetallic compound is 16.1 mg / g after 500 min, indicating that the material has excellent capacitive deionization performance.

Claims

1. A construction method of iron-cobalt intermetallic compound applied to capacitive deionization, characterized in that: The iron-cobalt intermetallic compound prepared by the method is nanoparticles coated with a carbon film. Cobalt and iron form a solid solution, and the valence state of cobalt is Co 0 、Co 2 + 、Co 3+ , and the valence state of iron is Fe 0 、Fe 2+ 、Fe 3+ ; At a voltage of 1.6 V and a sodium chloride concentration of 500 mg / L, the desalination capacity of the iron-cobalt intermetallic compound is 16.1 mg / g after 500 min; The method is completed according to the following steps: (1) At room temperature, 1 g of polyvinylpyrrolidone is added to 30 mL of deionized water and stirred for 1 hour to dissolve it, obtaining an aqueous solution of polyvinylpyrrolidone; (2) 1.05 g of cobalt nitrate and 0.45 g of iron nitrate are respectively added to the aqueous solution of polyvinylpyrrolidone in step (1). At room temperature, it is stirred for 5 hours to obtain solution A. Then, solution A is placed in an oven and dried at 95 °C for 24 hours; (3) 0.2 g of the dried product in step (2) is placed in a tubular furnace and calcined at 700 °C for 1 hour under the protection of N2. After cooling it to 100 °C, it is quenched with liquid nitrogen, and thus the iron-cobalt intermetallic compound material is obtained.

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