NiCoS hollow nanosphere rich in sulfur vacancies as well as preparation method and application of NiCoS hollow nanosphere

Abstract

The invention provides a preparation method of NiCoS hollow nanospheres rich in sulfur vacancies. The invention provides a preparation method of NiCoS hollow nanospheres rich in sulfur vacancies, which comprises the following steps: uniformly mixing nickel salt, cobalt salt, trimesic acid, polyvinylpyrrolidone and N, N-dimethylformamide, reacting to obtain a NiCo-MOF precursor, adding NiCo-MOF into a sulfur source solution, vulcanizing to obtain NiCoS hollow nanospheres, and drying to obtain the NiCoS hollow nanospheres rich in sulfur vacancies. And finally, the NiCoS nanospheres are put into argon and hydrogen mixed gas for reduction, and the NiCoS hollow nanospheres rich in sulfur vacancies are obtained. The number of active sites, the conductivity and the stability of the electrode material are increased by utilizing the synergistic effect of bimetals, construction of a hollow structure and introduction of sulfur vacancies. Practice shows that when the NiCoS hollow nanosphere rich in sulfur vacancies is used as a supercapacitor electrode material, the specific capacity and the rate capability are remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of electrode materials, and particularly relates to a method for preparing NiCoS hollow nanospheres rich in sulfur vacancies. Background Art

[0002] Supercapacitors have been widely used in various fields due to their high power density, good cycle stability and fast charge and discharge. The key to improving the performance of supercapacitors is to synthesize porous nanoelectrode materials with high performance and stability through simple, safe and economical methods.

[0003] Transition metal sulfides, such as cobalt sulfide and nickel sulfide, have the advantages of high theoretical capacitance and good environmental compatibility, and are ideal electrode materials for supercapacitors. However, single transition metal sulfide materials cannot meet the increasingly high practical needs due to their low conductivity and active sites, and the large volume changes that easily occur during redox reactions. Studies have shown that on the one hand, active sites and mass transfer efficiency can be increased by constructing porous micro-nano structures; on the other hand, defect engineering and the introduction of vacancies have been widely used to regulate electronic structure and state and generate abundant electrochemical sites to improve electrochemical performance. Summary of the invention

[0004] In order to solve the above technical problems, the present invention adopts a simple and low-cost preparation method to realize the preparation of NiCoS hollow nanospheres rich in sulfur vacancies. First, the use of nickel-cobalt bimetallic as a metal source effectively improves the problem of insufficient redox reaction of a single metal; secondly, the hollow nanosphere structure derived from a metal organic framework (MOF) is used to fully expose the active sites and alleviate the volume change during the reaction; finally, the further modification of sulfur vacancies improves the conductivity of the material, changes the built-in electric field, and thus improves the energy storage capacity of the material. Therefore, NiCoS hollow nanospheres rich in sulfur vacancies are generally applicable to the field of supercapacitors and are an ideal electrode material.

[0005] The present invention provides a method for preparing NiCoS hollow nanospheres rich in sulfur vacancies, comprising the following steps:

[0006] (1) dissolving cobalt salt, nickel salt, trimesic acid, and polyvinyl pyrrolidone in N,N-dimethylformamide, and then reacting at 160° C. for 10 h, cooling to room temperature, washing, centrifuging, and drying to obtain a NiCo-MOF precursor;

[0007] (2) adding the NiCo-MOF precursor prepared in step (1) into 30 mL of anhydrous ethanol solution containing a sulfur source, and sulfurizing to obtain NiCoS hollow nanospheres;

[0008] (3) The NiCoS hollow nanospheres prepared in step (2) were spread flat on a porcelain boat and placed in a tube furnace. After the air was exhausted by introducing a mixture of argon and hydrogen, the temperature was raised to the reaction temperature at a rate of 5°C / min and kept at this temperature for 30 min. After cooling to room temperature, NiCoS hollow nanospheres rich in sulfur vacancies were obtained, referred to as V S -NiCoS.

[0009] In the step (1), the type of cobalt salt is not limited, including cobalt chloride, cobalt nitrate, cobalt acetate, etc., but cobalt nitrate hexahydrate is most preferred; the type of nickel salt is not limited, including nickel chloride, nickel nitrate, nickel sulfate, etc., but nickel nitrate hexahydrate is most preferred.

[0010] In the step (1), the molar ratio of cobalt nitrate hexahydrate to nickel nitrate hexahydrate is (0.3-3):1, but the optimal ratio is 0.5:1.

[0011] In the step (1), the volume of N,N-dimethylformamide used is 50-100 mL, but most preferably 60 mL.

[0012] In step (2), the type of sulfur source is not limited, including one or more of sodium sulfide, thiourea, and thioacetamide, but thioacetamide is most preferred.

[0013] In the step (2), the vulcanization temperature is 120-160° C., and the vulcanization time is 4-8 hours, but the most preferred reaction time is 6 hours at 160° C.

[0014] In the step (3), the hydrogen content in the argon-hydrogen mixed gas is 2-15%, but most preferably 5%.

[0015] In the step (3), the reaction temperature is 250-400°C, but most preferably 300°C.

[0016] In summary, the NiCoS hollow nanospheres rich in sulfur vacancies of the present invention have the following beneficial effects:

[0017] (1) Preparation of V S -NiCoS requires low raw material cost and simple synthesis process, which only requires solvent thermal synthesis and argon-hydrogen mixed gas reduction. S -NiCoS has good electrical conductivity; the hollow nanosphere structure can fully expose the active sites and alleviate the volume change during the reaction; the introduction of sulfur vacancies changes the built-in electric field of the material, thereby generating more abundant electron transmission channels, reducing the energy barrier for redox reactions, and fully enhancing the synergistic effect between the components.

[0018] (2) V prepared by the present invention S-NiCoS, demonstrated 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 1520.4F / g, and even at a current density of 10A / g, the electrode material has a specific capacitance of 840F / g, with good rate performance.

[0019] (3) The preparation method of the present invention is simple and efficient, demonstrating the positive influence of structure and vacancy regulation on the construction of metal sulfide electrode materials, and can be easily extended to construct high-performance electrode materials for other energy storage and conversion devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a scanning electron microscope image of the NiCo-MOF precursor prepared in Example 1 of the present invention;

[0021] Figure 2 is a scanning electron microscope image of the NiCoS hollow nanospheres prepared in Example 1 of the present invention;

[0022] Figure 3 is V prepared in Example 1 of the present invention S -SEM image of NiCoS;

[0023] Figure 4 The NiCoS hollow nanospheres prepared in step (2) of Example 1 of the present invention and the V prepared in step (3) are S -X-ray diffraction pattern of NiCoS;

[0024] Figure 5 is V prepared in step (3) of Example 1 of the present invention S -Cyclic voltammetry curves of NiCoS as electrode material at different scan rates in 2MKOH electrolyte solution. The right figure is the charge and discharge curves at different current densities;

[0025] Figure 6 The NiCoS prepared in step (2) and the V prepared in step (3) in Example 1 of the present invention are S -Specific capacitance of NiCoS as electrode material in 2M KOH electrolyte solution. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention are described in further detail below with reference to the accompanying drawings and examples.

[0027] Example 1

[0028] A method for preparing NiCoS hollow nanospheres rich in sulfur vacancies comprises the following steps:

[0029] (1) 1 mmol of cobalt nitrate hexahydrate, 2 mmol of nickel nitrate hexahydrate, 0.3 g of trimesic acid and 2.0 g of polyvinyl pyrrolidone were uniformly dissolved in 60 mL of N,N-dimethylformamide, and then reacted at 160 °C for 10 h. After cooling to room temperature, the precursor was washed, centrifuged and dried to obtain a NiCo-MOF precursor, the scanning electron microscopy image of which is shown in FIG. Figure 1 As shown, it presents a nanosphere morphology with uniform particle size;

[0030] (2) 0.1 g NiCo-MOF and 0.15 g thioacetamide were dispersed in 30 mL anhydrous ethanol for sulfidation reaction at 160 °C for 6 h. After the reaction, NiCoS hollow nanospheres were obtained by washing, centrifugation and drying. The scanning electron microscopy results are as follows: Figure 2 As shown, it presents a nanosphere structure with a rough surface and a hollow interior;

[0031] (3) 0.04 g of NiCoS hollow nanospheres were spread flat in a porcelain boat and placed in a tube furnace. After the air was exhausted by introducing an argon-hydrogen mixed gas (hydrogen content was 5%), the temperature was raised to 300°C at a rate of 5°C / min, and kept at 300°C for 30 min. After cooling to room temperature, NiCoS hollow nanospheres rich in sulfur vacancies were obtained, referred to as V S -NiCoS, its scanning electron microscope image is as follows Figure 3 As shown, it presents a nanosphere structure with a rough surface and a hollow interior.

[0032] The V prepared in the above steps S -X-ray diffraction pattern of NiCoS, such as Figure 4 As shown; the diffraction peaks are all attributed to CoNi 2 S 4 (JCPDS No.24-0334).

[0033] The V S -NiCoS was used as supercapacitor electrode material and its electrochemical performance was tested in 2M KOH electrolyte solution, such as Figure 5 The left figure is the cyclic voltammetry curve at different scan rates, and the right figure is the charge and discharge curve at different current densities.

[0034] The V S -NiCoS was used as a supercapacitor electrode material, and its specific capacitance at different current densities was tested in 2M KOH electrolyte solution, such as Figure 6 As shown, V s -NiCoS exhibits specific capacitances of 1520.4 F / g and 840 F / g at 1 A / g and 10 A / g, respectively, indicating that the electrochemical performance is greatly improved by modifying sulfur vacancies on the NiCo bimetallic nanospheres.

[0035] Example 2

[0036] (1) 2 mmol of cobalt nitrate hexahydrate, 1 mmol of nickel nitrate hexahydrate, 0.3 g of trimesic acid and 2.0 g of polyvinyl pyrrolidone were uniformly dissolved in 60 mL of N,N-dimethylformamide, and then reacted at 160 °C for 10 h. After cooling to room temperature, the mixture was washed, centrifuged and dried to obtain a NiCo-MOF precursor.

[0037] (2) 0.1 g NiCo-MOF and 0.18 g sodium sulfide were dispersed in 40 mL anhydrous ethanol for sulfidation reaction at 160 °C for 8 h. After the reaction, NiCoS hollow nanospheres were obtained by washing, centrifugation and drying.

[0038] (3) 0.04 g of NiCoS hollow nanospheres were spread flat in a porcelain boat and placed in a tube furnace. After the air was exhausted by introducing an argon-hydrogen mixed gas (hydrogen content was 5%), the temperature was raised to 300°C at a rate of 5°C / min, and kept at 300°C for 30 min. After cooling to room temperature, NiCoS hollow nanospheres rich in sulfur vacancies were obtained, referred to as V S -NiCoS.

[0039] The obtained V S -NiCoS was used as a supercapacitor electrode material, and its specific capacitance at different current densities was tested in a 2M KOH electrolyte solution. The electrode material had a specific capacitance of 1000.4 F / g at 1 A / g.

[0040] Example 3

[0041] (1) 1 mmol of cobalt nitrate hexahydrate, 2 mmol of nickel nitrate hexahydrate, 0.3 g of trimesic acid and 2.0 g of polyvinyl pyrrolidone were uniformly dissolved in 60 mL of N,N-dimethylformamide, and then reacted at 160 °C for 10 h. After cooling to room temperature, the mixture was washed, centrifuged and dried to obtain a NiCo-MOF precursor.

[0042] (2) 0.1 g NiCo-MOF and 0.15 g thioacetamide were dispersed in 30 mL anhydrous ethanol for sulfidation reaction at 160 °C for 6 h. After the reaction, NiCoS hollow nanospheres were obtained by washing, centrifugation and drying.

[0043] (3) 0.04 g of NiCoS hollow nanospheres were spread flat on a porcelain boat and placed in a tube furnace. After the air was exhausted by introducing an argon-hydrogen mixed gas (hydrogen content was 8%), the temperature was raised to 350°C at a rate of 5°C / min, and the temperature was kept at 350°C for 60 min. After cooling to room temperature, NiCoS hollow nanospheres rich in sulfur vacancies were obtained, referred to as V S-NiCoS.

[0044] The obtained V S -NiCoS is used as a supercapacitor electrode material. Its specific capacitance at different current densities is tested in a 2M KOH electrolyte solution. The electrode material has a specific capacitance of 1216.7F / g at 1A / g.

[0045] Example 4

[0046] (1) 1 mmol of cobalt nitrate hexahydrate, 2 mmol of nickel nitrate hexahydrate, 0.3 g of trimesic acid and 2.0 g of polyvinyl pyrrolidone were uniformly dissolved in 60 mL of N,N-dimethylformamide, and then reacted at 160 °C for 10 h. After cooling to room temperature, the mixture was washed, centrifuged and dried to obtain a NiCo-MOF precursor.

[0047] (2) 0.05 g NiCo-MOF and 0.10 g thioacetamide were dispersed in 30 mL anhydrous ethanol for sulfidation reaction at 160 °C for 86 h. After the reaction, NiCoS hollow nanospheres were obtained by washing, centrifugation and drying.

[0048] (3) 0.05 g of NiCoS hollow nanospheres were spread flat on a porcelain boat and placed in a tube furnace. After the air was exhausted by introducing an argon-hydrogen mixed gas (hydrogen content was 3%), the temperature was raised to 250°C at a rate of 5°C / min, and the temperature was kept at 250°C for 30 min. After cooling to room temperature, NiCoS hollow nanospheres rich in sulfur vacancies were obtained, referred to as V S -NiCoS.

[0049] The obtained V S -NiCoS was used as a supercapacitor electrode material, and its specific capacitance at different current densities was tested in a 2M KOH electrolyte solution. The electrode material had a specific capacitance of 1189.2 F / g at 1 A / g.

[0050] Example 5

[0051] (1) 1 mmol of cobalt nitrate hexahydrate, 2 mmol of nickel nitrate hexahydrate, 0.3 g of trimesic acid and 2.0 g of polyvinyl pyrrolidone were uniformly dissolved in 60 mL of N,N-dimethylformamide, and then reacted at 160 °C for 10 h. After cooling to room temperature, the mixture was washed, centrifuged and dried to obtain a NiCo-MOF precursor.

[0052] (2) 0.1 g NiCo-MOF and 0.15 g thiourea were dispersed in 30 mL anhydrous ethanol for sulfidation reaction at 120 °C for 2 h. After the reaction, NiCoS hollow nanospheres were obtained by washing, centrifugation and drying.

[0053] (3) 0.05 g of NiCoS hollow nanospheres were spread flat on a porcelain boat and placed in a tube furnace. Argon-hydrogen mixed gas (hydrogen content was 5%) was introduced for 30 min. After exhausting the air, the temperature was raised to 350°C at a rate of 5°C / min, kept at 350°C for 30 min, and cooled to room temperature to obtain NiCoS hollow nanospheres rich in sulfur vacancies, referred to as V. S -NiCoS.

[0054] V S -NiCoS was used as a supercapacitor electrode material, and its specific capacitance at different current densities was tested in a 2M KOH electrolyte solution. The electrode material had a specific capacitance of 1222.4 F / g at 1 A / g.

[0055] 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 NiCoS hollow nanospheres rich in sulfur vacancies, It is characterized in that The preparation method comprises the following steps: (1) 1 mmol of cobalt nitrate hexahydrate, 2 mmol of nickel nitrate hexahydrate, 0.3 g of trimesic acid and 2.0 g of polyvinyl pyrrolidone were uniformly dissolved in 60 mL of N,N-dimethylformamide, and then reacted at 160 °C for 10 h. After cooling to room temperature, the mixture was washed, centrifuged and dried to obtain a NiCo-MOF precursor. (2) 0.1 g NiCo-MOF and 0.15 g thioacetamide were dispersed in 30 mL anhydrous ethanol for sulfidation reaction at 160 °C for 6 h. After the reaction, NiCoS hollow nanospheres were obtained by washing, centrifugation and drying. (3) 0.04 g of NiCoS hollow nanospheres were spread flat in a porcelain boat and placed in a tubular furnace. After the air was exhausted by passing an argon-hydrogen mixed gas, the temperature was raised to 300 °C at a rate of 5 °C / min and kept at 300 °C for 30 min. After cooling to room temperature, NiCoS hollow nanospheres rich in sulfur vacancies were obtained.

2. Use of NiCoS hollow nanospheres rich in sulfur vacancies obtained by the preparation method according to claim 1 as supercapacitor electrode materials.

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