A Se-doped NiCo 2 O 4 Materials, preparation methods and applications thereof

Abstract

The present invention provides a Se-doped NiCo2O4 material, a preparation method thereof and an application thereof. The method comprises the following steps: First, hexamethylenetetramine, Co(NO3)2·6H2O and Ni(NO3)2·6H2O are dissolved in a mixed solvent of deionized water and ethanol, and then transferred to an autoclave for heating reaction; after the reaction is completed, the reaction precipitate is washed and heated for drying to obtain a NiCo precursor; then the NiCo precursor is dissolved in deionized water, Na2SeO3 and N2H4·H2O are added, and the mixture is transferred to an autoclave and reacted at a temperature of 160-200 °C for 12-24 h, cooled to room temperature, and the product is washed and dried to obtain the Se-doped NiCo2O4 material. The raw materials of the invention are cheap and easy to obtain, the synthesis process is simple and easy to implement, the product quality is stable and the process repeatability is good; moreover, the cobalt nickel oxide electrode material doped with selenium effectively improves the redox activity, specific capacity and electron transport ability of the electrode material, has excellent charge storage ability, exhibits excellent supercapacitor performance, and can be applied to the electrode material of supercapacitors.

Description

Technical Field

[0001] The present invention belongs to the technical field of supercapacitor electrode materials, and in particular relates to a Se-doped NiCo2O4 material and a preparation method and application thereof. Background Art

[0002] In recent years, supercapacitors have attracted extensive attention due to their many advantages, including fast charge and discharge kinetics, long cycle life, and high power density.

[0003] Electrode materials play a vital role in the performance of supercapacitors. The active electrode materials currently studied include: carbon materials, transition metal oxides and hydroxides, conductive polymers, metal halides, etc. Among them, transition metal oxides (such as RuO2, MnO2, Co3O4, NiCo2O4) have attracted more attention from researchers due to their low price and excellent performance, and NiCo2O4 has high conductivity and high specific volume, making it a hot spot of research. In order to improve the performance of nickel cobalt oxide, researchers have adopted many preparation methods such as sol-gel, hydrothermal, and electrodeposition to prepare nickel cobalt oxide electrode materials with various morphologies and structures. However, there is no report on the use of selenium doping to improve the cycle stability and electrochemical properties of nickel cobalt oxide electrode materials and their use in supercapacitor electrode materials. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing Se-doped NiCo2O4 material, which can at least solve some of the defects existing in the prior art.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] A method for preparing Se-doped NiCo2O4 material comprises the following steps:

[0007] S1. Dissolve urotropine, Co(NO3)2·6H2O and Ni(NO3)2·6H2O in a mixed solvent of deionized water and ethanol, and stir thoroughly to form a mixed solution A;

[0008] S2, transferring the mixed solution A to an autoclave for heating reaction;

[0009] S3, after the heating reaction is completed, the reaction precipitate is washed multiple times with deionized water and ethanol, and then the washed reaction precipitate is vacuum heated and dried to obtain a NiCo precursor;

[0010] S4, dissolving the NiCo precursor in deionized water, adding Na2SeO3 and N2H4·H2O to disperse in the NiCo precursor solution, and stirring thoroughly to form a mixed solution B;

[0011] S5. Transfer the mixed solution B to an autoclave, react at 160-200°C for 12-24h, cool naturally to room temperature, centrifuge the obtained product and wash it with deionized water and ethanol, and then dry the washed product at a constant temperature to obtain Se-doped NiCo2O4 material.

[0012] Furthermore, in step S1, the molar ratio of urotropine, Co(NO3)2·6H2O, and Ni(NO3)2·6H2O is (5-0.5):2:1, and the volume ratio of deionized water and ethanol in the mixed solvent is 1:1-3:1.

[0013] Furthermore, in step S2, the reaction temperature of the mixed solution A is 80-110° C., and the reaction time is 5-8 h.

[0014] Furthermore, in step S3, the vacuum drying temperature is 50-65° C., and the drying time is 10-15 hours.

[0015] Furthermore, in step S4, the mass ratio of Na2SeO3 to NiCo precursor is (1-10):50, and the mass volume ratio of Na2SeO3 to N2H4·H2O is (1-10) mg:(0.1-0.5) ml.

[0016] Furthermore, in step S5, the product after washing is dried at a constant temperature of 50 to 65° C. for 10 to 15 hours.

[0017] In addition, the present invention also provides a Se-doped NiCo2O4 material, which is prepared by the above-mentioned preparation method.

[0018] Furthermore, the Se doping amount in the Se-doped NiCo2O4 material is 1-10%.

[0019] Furthermore, the Se-doped NiCo2O4 material is a nanosheet structure.

[0020] The present invention also provides the use of the Se-doped NiCo2O4 material as an electrode material in a supercapacitor.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The preparation method of the Se-doped NiCo2O4 material provided by the present invention firstly adopts a hydrothermal method to synthesize a NiCo precursor, and then utilizes Na2SeO3 and N2H4·H2O to react with the NiCo precursor to synthesize a selenium-doped NiCo2O4 material. The raw materials of the preparation method are cheap and easy to obtain, the synthesis process is simple and easy to implement, the product quality is stable and the process repeatability is good; and the selenium-doped nickel cobalt oxide electrode material is utilized to effectively improve the redox activity, specific capacity and electron transmission capacity of the electrode material, has excellent charge storage capacity, exhibits excellent supercapacitor performance, and can be applied to the electrode material of the supercapacitor.

[0023] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a SEM image of the Se-doped NiCo2O4 material prepared in an embodiment of the present invention;

[0025] Figure 2 is a high magnification SEM image of the Se-doped NiCo2O4 material prepared in an embodiment of the present invention;

[0026] Figure 3 is the XRD pattern of the Se-doped NiCo2O4 material prepared in the embodiment of the present invention;

[0027] Figure 4 is a comparison diagram of CV curves of four different electrode materials in an embodiment of the present invention;

[0028] Figure 5 is a comparison diagram of GCD curves of four different electrode materials in an embodiment of the present invention;

[0029] Figure 6 is a comparison chart of the specific capacities of four different electrode materials at different current densities in an embodiment of the present invention;

[0030] Figure 7 1 is an EIS graph of four different electrode materials in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In the examples of the present invention, unless otherwise specified, the technical terms used are commonly used by ordinary technicians in the field; the experimental methods in the examples of the present invention without specifying specific conditions are based on conventional experimental methods; the experimental materials used in the examples of the present invention are all commercially available products unless otherwise specified, and the ingredients and preparation methods of various reagents can refer to the operations in the conventional experimental manual.

[0033] Embodiment 1:

[0034] This embodiment provides a Se-doped NiCo2O4 material, and the specific preparation process is as follows:

[0035] S1. Dissolve 0.5 mol of urotropine, 2 mol of Co(NO3)2·6H2O, and 1 mol of Ni(NO3)2·6H2O in a mixed solvent of 10 ml of deionized water and 10 ml of ethanol, and stir vigorously for 15 min to form a mixed solution A.

[0036] S2. Transfer the mixed solution A to a 50 ml polytetrafluoroethylene-lined autoclave and heat at 80 °C for 8 h.

[0037] S3. After the heating reaction is completed, the reaction precipitate is washed 6 times with deionized water and ethanol, and then the washed reaction precipitate is vacuum dried at 50° C. for 15 h to obtain a NiCo precursor for use.

[0038] S4. Take 50 mg of NiCo precursor and dissolve it in 25 ml of deionized water. Then add 1 mg of Na2SeO3 and 0.1 ml of N2H4·H2O and disperse them in the NiCo precursor solution. Stir well for 30 min to form a mixed solution B.

[0039] S5. Transfer the mixed solution B to an autoclave, react at 160°C for 20 hours, cool naturally to room temperature, centrifuge the obtained product and wash it with deionized water and ethanol, and then dry the washed product at 50°C for 15 hours to obtain Se-doped NiCo2O4 material.

[0040] Embodiment 2:

[0041] This embodiment provides a Se-doped NiCo2O4 material, and the specific preparation process is as follows:

[0042] S1. Dissolve 1 mol of urotropine, 2 mol of Co(NO3)2·6H2O, and 1 mol of Ni(NO3)2·6H2O in a mixed solvent of 20 ml of deionized water and 10 ml of ethanol, and stir vigorously for 15 min to form a mixed solution A.

[0043] S2. Transfer the mixed solution A to a 50 ml polytetrafluoroethylene-lined autoclave and heat at 90 °C for 6 h.

[0044] S3. After the heating reaction is completed, the reaction precipitate is washed 6 times with deionized water and ethanol, and then the washed reaction precipitate is vacuum dried at 60° C. for 12 h to obtain a NiCo precursor for use.

[0045] S4. Take 50 mg of NiCo precursor and dissolve it in 25 ml of deionized water. Then add 3 mg of Na2SeO3 and 0.3 ml of N2H4·H2O and disperse them in the NiCo precursor solution. Stir well for 30 min to form a mixed solution B.

[0046] S5. Transfer the mixed solution B to an autoclave, react at 180°C for 18 hours, cool naturally to room temperature, centrifuge the obtained product and wash it with deionized water and ethanol, and then dry the washed product at 60°C for 12 hours to obtain Se-doped NiCo2O4 material.

[0047] The Se-doped NiCo2O4 material prepared in this example was subjected to electron microscope scanning, and the results are as follows: Figure 1 and Figure 2 As shown. Figure 1 From the SEM display, it can be seen that Se-doped NiCo2O4 material presents a nanosheet structure, which has a large specific surface area and can provide an effective place for charge storage; Figure 2 High-magnification SEM shows that the surface of Se-doped NiCo2O4 material presents an uneven morphology, which is caused by Se doping. This uneven structure can provide more active sites for its redox reaction as an electrode material.

[0048] The Se-doped NiCo2O4 material prepared in this example was subjected to X-ray powder diffraction, and the results are as follows: Figure 3 As shown. Figure 3 It can be seen that the Se-doped NiCo2O4 material exhibits characteristic peaks (111), (220), (311), (400), (511), and (440), which match well with the characteristic peaks of JCPDS card 20-0781 of NiCo2O4, indicating that no detectable phase change occurs during the Se doping process.

[0049] Embodiment 3:

[0050] This embodiment provides a Se-doped NiCo2O4 material, and the specific preparation process is as follows:

[0051] S1. Dissolve 3 mol of urotropine, 2 mol of Co(NO3)2·6H2O, and 1 mol of Ni(NO3)2·6H2O in a mixed solvent of 25 ml of deionized water and 10 ml of ethanol, and stir vigorously for 15 min to form a mixed solution A.

[0052] S2. Transfer the mixed solution A to a 50 ml polytetrafluoroethylene-lined autoclave and heat at 100 °C for 5.5 h.

[0053] S3. After the heating reaction is completed, the reaction precipitate is washed 6 times with deionized water and ethanol, and then the washed reaction precipitate is vacuum dried at 60° C. for 12 h to obtain a NiCo precursor for use.

[0054] S4. Take 50 mg of NiCo precursor and dissolve it in 25 ml of deionized water. Then add 5 mg of Na2SeO3 and 0.5 ml of N2H4·H2O and disperse them in the NiCo precursor solution. Stir well for 30 min to form a mixed solution B.

[0055] S5. Transfer the mixed solution B to an autoclave, react at 180°C for 24 hours, cool naturally to room temperature, centrifuge the obtained product and wash it with deionized water and ethanol, and then dry the washed product at 60°C for 12 hours to obtain Se-doped NiCo2O4 material.

[0056] Embodiment 4:

[0057] This embodiment provides a Se-doped NiCo2O4 material, and the specific preparation process is as follows:

[0058] S1. Dissolve 5 mol of urotropine, 2 mol of Co(NO3)2·6H2O, and 1 mol of Ni(NO3)2·6H2O in a mixed solvent of 30 ml of deionized water and 10 ml of ethanol, and stir vigorously for 15 min to form a mixed solution A.

[0059] S2. Transfer the mixed solution A to a 50 ml polytetrafluoroethylene-lined autoclave and heat at 110 °C for 5 h.

[0060] S3. After the heating reaction is completed, the reaction precipitate is washed 6 times with deionized water and ethanol, and then the washed reaction precipitate is vacuum dried at 65° C. for 10 h to obtain a NiCo precursor for use.

[0061] S4. Take 50 mg of NiCo precursor and dissolve it in 25 ml of deionized water. Then add 10 mg of Na2SeO3 and 0.5 ml of N2H4·H2O and disperse them in the NiCo precursor solution. Stir well for 30 min to form a mixed solution B.

[0062] S5. Transfer the mixed solution B to an autoclave, react at 200°C for 12 h, cool naturally to room temperature, centrifuge the obtained product and wash it with deionized water and ethanol, and then dry the washed product at 65°C for 10 h to obtain Se-doped NiCo2O4 material.

[0063] Embodiment 5:

[0064] In this example, the electrochemical performance of the Se-doped NiCo2O4 material of the present invention as an electrode material was studied in a 3M KOH electrolyte under a three-electrode system.

[0065] The undoped NiCo2O4 material and the Se-doped NiCo2O4 material prepared in the above Examples 1 to 3 (respectively denoted as Se-NiCo2O4-1, Se-NiCo2O4-2, and Se-NiCo2O4-3) were subjected to the same scanning rate (5 mV·s -1 ) under the CV curve is as follows Figure 4 As shown. Figure 4 It can be seen that a pair of obvious redox peaks can be observed in the CV curves of the four materials, which is a characteristic of battery-type electrode materials, indicating that the Se-doped NiCo2O4 material of the present invention can be used as an electrode material; and, compared with the NiCo2O4 material not doped with Se, the closed area of ​​the CV curve of the Se-doped NiCo2O4 material (i.e., Se-NiCo2O4-1, Se-NiCo2O4-2, Se-NiCo2O4-3) prepared by the present invention is significantly larger, indicating that Se doping can effectively improve the redox activity of the electrode material and is more conducive to the electrochemical reaction; at the same time, the CV curve closed area of ​​Se-NiCo2O4-2 is the largest, indicating its excellent charge storage capacity, which can also be shown that the Se doping amount in the Se-doped NiCo2O4 material will affect its charge storage capacity. After multiple experimental analyses, the present invention selects the Se doping amount in the Se-doped NiCo2O4 material to be 1 to 10%.

[0066] The undoped NiCo2O4 material and the Se-doped NiCo2O4 material prepared in the above Examples 1 to 3 (respectively denoted as Se-NiCo2O4-1, Se-NiCo2O4-2, and Se-NiCo2O4-3) were subjected to the same current density (1 A·g -1 ) under constant current charge and discharge (GCD) curve as shown Figure 5 As shown. Figure 5It can be seen that the GCD curves of the four materials all have an obvious charge-discharge platform, indicating the pseudocapacitive characteristics of the samples, which is a typical feature of battery-type Faraday electrode materials, further indicating that the Se-doped NiCo2O4 material of the present invention can be used as an electrode material for supercapacitors; at the same time, Se-NiCo2O4-2 has the longest discharge time, indicating that it has the best charge storage capacity, which is consistent with the above CV curve results.

[0067] The specific capacities of the undoped NiCo2O4 material and the Se-doped NiCo2O4 material prepared in Examples 1 to 3 (respectively referred to as Se-NiCo2O4-1, Se-NiCo2O4-2, and Se-NiCo2O4-3) at different current densities are as follows: Figure 6 As shown. Figure 6 It can be seen that at 1A·g -1 At a current density of 1.34 W·m, the specific capacities of NiCo2O4, Se-NiCo2O-1, Se-NiCo2O-2 and Se-NiCo2O-3 were 1126.5 F·g -1 , 1590.6F·g -1 , 2004.6F·g -1 and 1725.8F·g -1 The specific capacity of the sample doped with selenium (Se) increased significantly when the current density increased to 20A·g -1 When the sample was doped with selenium, the specific capacity retention rates of NiCo2O4, Se-NiCo2O-1, Se-NiCo2O-2 and Se-NiCo2O-3 were 56.4%, 57.9%, 64.3% and 61.7%, respectively. It can be seen that the rate performance of the samples doped with selenium increased, indicating that the electron transport ability of the selenium-doped electrode material was enhanced.

[0068] The electron transfer ability of the above-mentioned undoped NiCo2O4 material and the Se-doped NiCo2O4 materials prepared in the above-mentioned Examples 1 to 3 (respectively denoted as Se-NiCo2O4-1, Se-NiCo2O4-2, and Se-NiCo2O4-3) as electrode surfaces was studied by electrochemical impedance spectroscopy (EIS). The results are as follows: Figure 7 As shown. Figure 7 It can be seen that the Nernst diagrams of NiCo2O4, Se-NiCo2O4-1, Se-NiCo2O4-2, and Se-NiCo2O4-3 are composed of high-frequency quasi-semicircle and low-frequency linear parts. The intersection of the high-frequency quasi-semicircle part and the real axis represents the electrode internal resistance (RS), which is generated by the electrolyte ion resistance, the electrode internal resistance, and the interface ohmic resistance between the active material and the electrolyte. The semicircle diameter of the high-frequency quasi-semicircle part corresponds to the charge transfer resistance (R ct), which is related to the charge transfer speed. The slope of the line in the low-frequency linear part mainly describes the diffusion capacity of the redox species in the electrolyte, that is, the Warburg resistance frequency. Figure 7 It can be seen that the Rs values ​​of NiCo2O4, Se-NiCo2O4-1, Se-NiCo2O4-2, and Se-NiCo2O4-3 are 0.61, 0.39, 0.17, and 0.35, respectively. Compared with NiCo2O4, the Rs values ​​of the samples doped with selenium (i.e., Se-NiCo2O4-1, Se-NiCo2O4-2, and Se-NiCo2O4-3) are significantly lower than those of NiCo2O4, indicating that selenium doping improves electronic conductivity. ct The value is also significantly lower than that of NiCo2O4, indicating that the charge transfer kinetics of the samples doped with Selenium is enhanced; in addition, Figure 7 It can also be seen that for the low-frequency linear part of NiCo2O4, Se-NiCo2O4-1, Se-NiCo2O4-2, and Se-NiCo2O4-3, compared with NiCo2O4, the slope of the low-frequency linear part of the samples doped with selenium (i.e., Se-NiCo2O4-1, Se-NiCo2O4-2, and Se-NiCo2O4-3) becomes steeper, indicating that the diffusion rate of ions in the electrolyte is accelerated; compared with other Se-NiCo2O4, Se-NiCo2O4-2 has the smallest semicircle diameter in the high-frequency region and the largest slope in the low-frequency region, indicating that Se-NiCo2O4-2 has the smallest impedance. This shows that the present invention uses an appropriate amount of selenium-doped NiCo2O4 to improve the conductivity of electrons and promote the occurrence of redox reactions of electrode materials.

[0069] In summary, the preparation method of the Se-doped NiCo2O4 material provided by the present invention first adopts a hydrothermal method to synthesize a NiCo precursor, and then uses Na2SeO3 and N2H4·H2O to react with the NiCo precursor to synthesize a selenium-doped NiCo2O4 material. The raw materials of the preparation method are cheap and easy to obtain, the synthesis process is simple and easy to implement, the product quality is stable and the process repeatability is good; and the selenium-doped nickel cobalt oxide electrode material is used to effectively improve the redox activity, specific capacity and electron transmission capacity of the electrode material, has excellent charge storage capacity, exhibits excellent supercapacitor performance, and can be applied to the electrode material of supercapacitors.

[0070] The above examples are merely illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing Se-doped NiCo2O4 material, characterized in that: The steps include: S1. Dissolve urotropine, Co(NO3)2·6 H2O and Ni(NO3)2·6 H2O in a mixed solvent of deionized water and ethanol, and stir thoroughly to form a mixed solution A; S2, transferring the mixed solution A to an autoclave for heating reaction; S3, after the heating reaction is completed, the reaction precipitate is washed multiple times with deionized water and ethanol, and then the washed reaction precipitate is vacuum heated and dried to obtain a NiCo precursor; S4. Dissolve the NiCo precursor in deionized water, then add Na2SeO3 and N2H4·H2O to disperse in the NiCo precursor solution, and stir thoroughly to form a mixed solution B; wherein the mass ratio of Na2SeO3 to the NiCo precursor is (1-10):50, and the mass volume ratio of Na2SeO3 to N2H4·H2O is (1-10) mg:(0.1-0.5) ml; S5. Transfer the mixed solution B to an autoclave, react at 160-200° C. for 12-24 hours, cool naturally to room temperature, centrifuge the obtained product and wash it with deionized water and ethanol, and then dry the washed product at a constant temperature to obtain a Se-doped NiCo2O4 material; the Se-doped NiCo2O4 material has a nanosheet structure, and its surface presents an uneven morphology, and is used as an electrode material. The Se doping amount in the Se-doped NiCo2O4 material is 1-10%.

2. The method for preparing Se-doped NiCo2O4 material according to claim 1, characterized in that: In the step S1, the molar ratio of hexamethylenetetramine, Co(NO3)2·6 H2O and Ni(NO3)2·6 H2O is (5-0.5):2:1, and the volume ratio of deionized water and ethanol in the mixed solvent is 1:1-3:

1.

3. The method for preparing Se-doped NiCo2O4 material according to claim 1, characterized in that: In the step S2, the reaction temperature of the mixed solution A is 80-110° C., and the reaction time is 5-8 hours.

4. The method for preparing Se-doped NiCo2O4 material according to claim 1, characterized in that: In step S3, the vacuum drying temperature is 50-65° C., and the drying time is 10-15 hours.

5. The method for preparing Se-doped NiCo2O4 material according to claim 1, characterized in that: In step S5, the product after washing is dried at a constant temperature of 50 to 65° C. for 10 to 15 hours.

6. A Se-doped NiCo2O4 material, characterized in that: The method is prepared by the method according to any one of claims 1 to 5.

7. A supercapacitor, characterized in that: The Se-doped NiCo2O4 material according to claim 6 is used as the electrode material.

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