CN111573743A

CN111573743A - Double-layer hollow dodecahedron zinc-cobalt-based sulfide composite material and preparation method thereof

Info

Publication number: CN111573743A
Application number: CN202010341274.2A
Authority: CN
Inventors: 张淮浩; 侯双月; 柏永青; 练越; 周秋平; 赵静
Original assignee: Yangzhou University
Current assignee: Yangzhou University
Priority date: 2020-04-27
Filing date: 2020-04-27
Publication date: 2020-08-25
Anticipated expiration: 2040-04-27
Also published as: CN111573743B

Abstract

The invention discloses a double-layer hollow dodecahedron zinc-cobalt-based sulfide composite material and a preparation method thereof, wherein zinc nitrate hexahydrate and cobalt nitrate hexahydrate are used as precursors to obtain ZIF-67 and ZIF-8 templates, and finally thioacetamide is used for vulcanizing the templates through a hydrothermal synthesis method to obtain double-layer cobaltosic sulfide @ zinc sulfide. According to the invention, the zinc-cobalt-based composite sulfide with a double-layer hollow structure is synthesized by using the MOF material, the double-layer structure effectively relieves the volume effect of the material and alleviates the problem of poor stability of the material, meanwhile, the hollow heterostructure can shorten the diffusion distance of ions, so that the electrochemical performance of the material is improved, and the synergistic effect among the heterogeneous materials can effectively increase the capacitance performance of the material.

Description

Double-layer hollow dodecahedron zinc-cobalt-based sulfide composite material and preparation method thereof

Technical Field

The invention relates to the technical field of electrode materials of supercapacitors, in particular to a preparation method of a double-layer hollow dodecahedron zinc-cobalt-based sulfide composite material.

Background

Super capacitor has high power density, fast charge and discharge rate, long cycle life and wide working temperature range. Supercapacitors can be classified into double layer capacitors and pseudocapacitors according to different energy storage mechanisms. The electric double layer capacitor stores electricity mainly by the adsorption of electrostatic charges on the surface of an electrode, and the pseudocapacitor stores energy by the generation of faradaic capacitance through the oxidation-reduction reaction of the surface material of the electrode.

The structure and the morphology of the material have obvious influence on the electrochemical performance of the material, and the hollow micro-nano particles are paid more and more attention due to the advantages of low density, high specific surface area, good permeability, short charge diffusion path and the like. Metal Organic Frameworks (MOFs) are a new class of porous materials consisting of metal ions and organic ligands. The preparation method is simple in preparation process, has a unique porous structure, is widely used as a template and a precursor for preparing a hollow structure material, and is an important research object in the fields of photocatalysis, solar energy, solid oxide fuel cells, supercapacitors and the like. Transition metal sulfides are widely researched due to the advantages of high theoretical specific capacitance, high energy density, low cost and the like, and the synthesis of transition metal sulfides by taking MOF as a template is a hot spot of the current research. However, in practical applications, there are still some problems that the single transition metal sulfide is still difficult to achieve the ideal state in terms of conductivity and cycling stability, thus leading to the practical specific capacitance value far lower than the theoretical value, and further limiting the application.

Disclosure of Invention

The invention aims to provide a double-layer hollow dodecahedral zinc-cobalt-based sulfide composite material for a super capacitor and a preparation method thereof, wherein zinc nitrate hexahydrate and cobalt nitrate hexahydrate are used as precursors to obtain ZIF-67 and ZIF-8 templates, and finally thioacetamide is used for vulcanizing the templates through a hydrothermal synthesis method to obtain double-layer cobaltosic sulfide @ zinc sulfide.

In order to solve the technical problems, the invention provides the double-layer hollow dodecahedral zinc-cobalt-based sulfide composite material and the preparation method thereof, and the method comprises the following specific steps:

1) preparation of 2L-ZIF-8@67

Uniformly dispersing ZIF-8@ ZIF-67 in methanol, adding zinc nitrate hexahydrate, continuously stirring, completely dissolving, adding a methanol solution of 2-methylimidazole, stirring at room temperature for 24 hours, collecting obtained products, centrifugally washing, and drying in an oven at 60 ℃ at the middle of a night to obtain a ZIF-8@ ZIF-67@ ZIF-8 precipitate; dispersing the obtained precipitate in methanol, performing ultrasonic treatment for 30 min to form uniform suspension, adding cobalt nitrate hexahydrate into the suspension, continuously stirring, adding a methanol solution of 2-methylimidazole after complete dissolution, stirring at room temperature for 24 h, collecting the precipitate by a centrifugal method, repeatedly washing, and finally drying in an oven at 60 ℃ overnight to obtain ZIF-8@ ZIF-67@ ZIF-8@ ZIF-67, which is named as 2L-ZIF-8@ 67;

2) preparation of 2L-ZnCoS

Dispersing the 2L-ZIF-8@67 obtained in the step 1) into ethanol, ultrasonically dispersing for 30 min, adding Thioacetamide (TAA), stirring for 20 min, transferring the obtained uniform suspension into a 100 mL hydrothermal reaction kettle with a polytetrafluoroethylene lining, heating at 100-200 ℃ for 60-120 min, naturally cooling to room temperature, collecting black precipitate by a centrifugal method, repeatedly washing with deionized water and ethanol, and finally drying at 60 ℃ overnight to obtain a product zinc sulfide @ cobaltosic sulfide @ zinc sulfide @ cobaltosic sulfide, wherein the product is named as 2L-ZnCoS.

Preferably, in the step 1), the mass ratio of the ZIF-8 to the ZIF-67 in the ZIF-8@ ZIF-67 is 1: 1-3.

Preferably, in the step 1), the mass ratio of ZIF-8@ ZIF-67 to zinc nitrate hexahydrate is 1: 1-3; the mass ratio of the ZIF-8@ ZIF-67@ ZIF-8 to the cobalt nitrate hexahydrate is 1: 1-3.

Preferably, in the step 1), the concentration of zinc nitrate hexahydrate is 0.1-0.2mol L^-1Preferably 0.13 mol L^-1。

Preferably, in the step 1), the concentration of the cobalt nitrate hexahydrate is 3-7 mg mL^-1Preferably 4 to 6 mg mL^-1。

Preferably, in the step 2), the concentration of thioacetamide is 2-3 mg mL^-1Preferably 2.4 mg mL^-1。

Preferably, in the step 2), the mass ratio of the 2L-ZIF-8@67 to the thioacetamide is 1: 3.

In the step 2), the suspension is heated at 150 ℃ for 90 min.

Compared with the prior art, the invention has the beneficial effects that:

(1) the hollow structure can enable ions to enter the hollow cavity of the material, and the diffusion distance of the ions is shortened, so that the electrochemical performance of the material is improved;

(2) gaps between adjacent shell layers can effectively play a role in buffering, and the volume change of the material in the charging and discharging process is reduced;

(3) the zinc sulfide and the cobaltosic sulfide simultaneously participate in energy storage, and the synergistic effect between the zinc sulfide and the cobaltosic sulfide can enhance the conductivity of the material;

(4) the double-shell structure can constrain the electrolyte between the shells, and provides higher driving force for the oxidation-reduction reaction.

Drawings

FIG. 1 is a transmission electron micrograph of 2L-ZIF-8@67-1 synthesized in example 1.

FIG. 2 is a scanning electron micrograph of 2L-ZnCoS-1 synthesized in example 1.

FIG. 3 is a transmission electron micrograph of 2L-ZnCoS-1 synthesized in example 1.

FIG. 4 is an XRD pattern of 2L-ZnCoS-1 synthesized in example 1.

FIG. 5 is a scanning electron micrograph of 2L-ZnCoS-2 synthesized in example 2.

FIG. 6 is a transmission electron micrograph of 2L-ZnCoS-2 synthesized in example 2.

FIG. 7 is a transmission electron micrograph of 1L-ZnCoS synthesized in example 3.

FIG. 8 is a mapping chart of 2L-ZnCoS-1 synthesized in example 1.

FIG. 9 is an electron spectrum fit of XPS analysis survey spectra elements of 2L-ZnCoS-1 prepared in example 1.

FIG. 10 is a graph of specific capacitance for different current densities for 2L-ZnCoS-1 prepared in example 1, 2L-ZnCoS-2 prepared in example 2, and 1L-ZnCoS prepared in example 3.

FIG. 11 is a graph of 2L-ZnCoS-1 at 5A g of example 1^-1Current density lower cycle performance plot of (a).

FIG. 12 is a graph of energy density versus power density for the 2L-ZnCoS-1 assembled asymmetric supercapacitor made in example 1.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in detail below with reference to examples.

The invention synthesizes the double-layer hollow dodecahedral zinc-cobalt-based composite sulfide for the first time and uses the double-layer hollow dodecahedral zinc-cobalt-based composite sulfide as a super capacitor, and the unique heterostructure provides a new idea for the design of the electrode material structure. In the invention, the advantages of MOF materials and sulfides are comprehensively utilized, a simple method is provided, and the multilayer composite sulfide with a hollow structure is synthesized. ZIF-8 and ZIF-67 are used as templates, and then Thioacetamide (TAA) is used for vulcanizing the templates to obtain double-layer zinc sulfide @ cobaltosic sulfide, and the electrochemical performance of the material is improved by constructing a unique hollow heterostructure.

According to the invention, the zinc-cobalt-based composite sulfide with a double-layer hollow structure is synthesized by using the MOF material, the double-layer structure effectively relieves the volume effect of the material, and the problem of poor stability of the material is alleviated, and meanwhile, the hollow heterostructure can shorten the diffusion distance of ions, thereby improving the electrochemical performance of the material. The synergistic effect between heterogeneous materials can effectively increase the capacitance performance of the material.

Example 1:

1) dissolving 4 mmol of zinc nitrate hexahydrate and 15 mmol of 2-methylimidazole in 30 mL and 10 mL of methanol respectively to form No. 1 solution and No. 2 solution, stirring for 10 minutes, quickly pouring the No. 1 solution into the No. 2 solution, stirring for 5 minutes vigorously, then stirring for 24 hours at room temperature, collecting the obtained white product, washing with methanol centrifugally for three times, and drying in an oven at 60 ℃ overnight to obtain ZIF-8. Dispersing 60 mg of the obtained ZIF-8 in 30 mL of methanol, performing ultrasonic treatment for 30 min to form uniform ZIF-8 suspension, then adding 160 mg of cobalt nitrate hexahydrate into the ZIF-8 suspension, continuing stirring, dissolving 300 mg of 2-methylimidazole in 10 mL of methanol during stirring, then quickly adding into the stirring suspension, stirring for 24 h at room temperature, collecting purple precipitate by a centrifugal method, repeatedly washing with methanol, and finally drying in an oven at 60 ℃ overnight to obtain the product ZIF-8@ ZIF-67. Uniformly dispersing 60 mg of ZIF-8@ ZIF-67 in 30 mL of methanol, adding 160 mg of zinc nitrate hexahydrate, continuously stirring, dissolving 300 mg of 2-methylimidazole in 10 mL of methanol during stirring, quickly adding into the stirring suspension, stirring at room temperature for 24 hours, collecting the obtained product, centrifugally washing for three times, and drying in an oven at 60 ℃ overnight to obtain a ZIF-8@ ZIF-67@ ZIF-8 precipitate. Dispersing 60 mg of the obtained ZIF-8@ ZIF-67@ ZIF-8 precipitate in 30 mL of methanol, performing ultrasonic treatment for 30 min to form uniform suspension, adding 160 mg of cobalt nitrate hexahydrate into the suspension, continuously stirring, dissolving 300 mg of 2-methylimidazole in 10 mL of methanol after complete dissolution, quickly adding the suspension into the stirring suspension, stirring for 24 h at room temperature, collecting the precipitate by a centrifugal method, repeatedly washing, and finally drying in an oven at 60 ℃ for a night to obtain the ZIF-8@ ZIF-67@ ZIF-8@ ZIF-67, which is named as 2L-ZIF-8@ 67-1.

The TEM image of the material is shown in FIG. 1, and it can be seen from FIG. 1 that 2L-ZIF-8@67-1 retains the dodecahedral structure of ZIF-8 and has a particle size of about 900 nm.

2) Dispersing 40 mg of the obtained 2L-ZIF-8@67-1 into 50 mL of ethanol, ultrasonically dispersing for 30 min, adding 120mg of Thioacetamide (TAA), stirring for 20 min, transferring the uniform suspension into a 100 mL of hydrothermal reaction kettle with a polytetrafluoroethylene lining, and heating at 150 ℃ for 90 min. Naturally cooling to room temperature, collecting black precipitate by a centrifugal method, repeatedly washing with deionized water and ethanol, and finally drying overnight at 60 ℃ to obtain a product of zinc sulfide @ cobaltosic sulfide @ zinc sulfide @ cobaltosic sulfide, which is named as 2L-ZnCoS-1.

SEM pictures and TEM pictures of the material are respectively shown in FIG. 2 and FIG. 3, and as can be seen from FIG. 2, 2L-ZnCoS-1 is a hollow structure; as can be seen from FIG. 3, 2L-ZnCoS-1 has a rough surface, which is advantageous in terms of the increase of the specific surface area.

FIG. 4 is an XRD pattern of 2L-ZnCoS-1 synthesized in example 1. As can be seen from fig. 4, the composite material had zinc sulfide and tricobalt tetrasulfide present.

FIG. 8 is a mapping chart of 2L-ZnCoS-1 prepared in example 1. In fig. 8, the core-shell structure of the material can be clearly seen, and the existence of three elements of Zn, Co and S is also proved.

FIG. 9 is an electron spectrum fit of XPS analysis survey spectra elements of 2L-ZnCoS-1 prepared in example 1. The presence of the elements Zn, Co, S is again demonstrated by FIG. 9.

Example 2:

1) 4 mmol of zinc nitrate hexahydrate and 15 mmol of 2-methylimidazole are dissolved in 30 mL and 10 mL of methanol respectively to form solution No. 1 and solution No. 2, and after stirring for 10 minutes, solution No. 1 is poured into solution No. 2 quickly. Vigorously stirred for five minutes, then stirred at room temperature for 24 h, the resulting white product was collected, washed three times with methanol centrifugation, and then dried in an oven at 60 ℃ overnight to obtain ZIF-8. Dispersing 60 mg of the obtained ZIF-8 in 30 mL of methanol, performing ultrasonic treatment for 30 min to form uniform ZIF-8 suspension, then adding 140 mg of cobalt nitrate hexahydrate into the ZIF-8 suspension, continuing stirring, dissolving 300 mg of 2-methylimidazole in 10 mL of methanol during stirring, then quickly adding into the stirring suspension, stirring for 24 h at room temperature, collecting purple precipitate by a centrifugal method, repeatedly washing with methanol, and finally drying in an oven at 60 ℃ overnight to obtain the product ZIF-8@ ZIF-67. Uniformly dispersing 60 mg of ZIF-8@ ZIF-67 in 30 mL of methanol, adding 160 mg of zinc nitrate hexahydrate, continuously stirring, dissolving 300 mg of 2-methylimidazole in 10 mL of methanol during stirring, quickly adding into the stirring suspension, stirring at room temperature for 24 hours, collecting the obtained product, centrifugally washing for three times, and drying in an oven at 60 ℃ overnight to obtain a ZIF-8@ ZIF-67@ ZIF-8 precipitate. Dispersing 60 mg of the obtained ZIF-8@ ZIF-67@ ZIF-8 precipitate in 30 mL of methanol, performing ultrasonic treatment for 30 min to form uniform suspension, adding 140 mg of cobalt nitrate hexahydrate into the suspension, continuously stirring, dissolving 300 mg of 2-methylimidazole in 10 mL of methanol after complete dissolution, quickly adding the suspension into the stirring suspension, stirring for 24 h at room temperature, collecting the precipitate by a centrifugal method, repeatedly washing, and finally drying in an oven at 60 ℃ for a night to obtain the ZIF-8@ ZIF-67@ ZIF-8@ ZIF-67, which is named as 2L-ZIF-8@ 67-2.

2) Dispersing 40 mg of the obtained 2L-ZIF-8@67-2 into 50 mL of ethanol, ultrasonically dispersing for 30 min, adding 120mg of Thioacetamide (TAA), stirring for 20 min, transferring the uniform suspension into a 100 mL of hydrothermal reaction kettle with a polytetrafluoroethylene lining, and heating at 150 ℃ for 90 min. Naturally cooling to room temperature, collecting black precipitate by a centrifugal method, repeatedly washing with deionized water and ethanol, and finally drying overnight at 60 ℃ to obtain a product of zinc sulfide @ cobaltosic sulfide @ zinc sulfide @ cobaltosic sulfide, which is named as 2L-ZnCoS-2.

SEM and TEM images of the material are shown in fig. 5 and 6, respectively, and the hollow structure of the material can be clearly seen.

Example 3:

1) dissolving 4 mmol of zinc nitrate hexahydrate and 15 mmol of 2-methylimidazole in 30 mL and 10 mL of methanol respectively to form No. 1 solution and No. 2 solution, stirring for 10 minutes, quickly pouring the No. 1 solution into the No. 2 solution, stirring for five minutes vigorously, then stirring for 24 hours at room temperature, collecting the obtained white product, washing with methanol centrifugally for three times, and drying in an oven at 60 ℃ overnight to obtain ZIF-8. Dispersing 60 mg of the obtained ZIF-8 in 30 mL of methanol, performing ultrasonic treatment for 30 min to form uniform ZIF-8 suspension, adding 160 mg of cobalt nitrate hexahydrate into the ZIF-8 suspension, continuously stirring, dissolving 300 mg of 2-methylimidazole in 10 mL of methanol during stirring, quickly adding the mixture into the stirring suspension, stirring for 24 h at room temperature, collecting precipitates by a centrifugal method, repeatedly washing the precipitates with methanol, and finally drying the precipitates in an oven at 60 ℃ overnight to obtain a product ZIF-8@ ZIF-67 which is named as 1L-ZIF-8@ 67.

2) Dispersing 40 mg of the obtained 1L-ZIF-8@67 in 50 mL of ethanol, ultrasonically dispersing for 30 min, adding 120mg of Thioacetamide (TAA), stirring for 20 min, transferring the uniform suspension to a 100 mL of hydrothermal reaction kettle with a polytetrafluoroethylene lining, and heating at 150 ℃ for 90 min. Naturally cooling to room temperature, collecting black precipitate by a centrifugal method, repeatedly washing with deionized water and ethanol, and finally drying at 60 ℃ overnight to obtain a product zinc sulfide @ cobaltosic sulfide, namely 1L-ZnCoS, wherein a TEM image of the material is shown in FIG. 7, and as can be seen from FIG. 7, the 1L-ZnCoS is a hollow structure with a shell.

The application comprises the following steps:

the electrode materials prepared in the three examples above were taken for parallel testing:

the composite material obtained in the example, the conductive agent and the binder were mixed in a mass ratio of 85:10:5 to prepare an electrode material. And (3) carrying out electrochemical performance test on the obtained electrode material through a three-electrode system, wherein the electrolyte is 6M KOH.

FIG. 10 is a graph of specific capacitance for different current densities for 2L-ZnCoS-1 prepared in example 1, 2L-ZnCoS-2 prepared in example 2, and 1L-ZnCoS prepared in example 3. As can be seen from FIG. 10, the 2L-ZnCoS-1 obtained in example 1, the 2L-ZnCoS-2 obtained in example 2 and the 1L-ZnCoS obtained in example 3 were each at 1A g^-1Specific capacitance of 1618.35F g respectively at specific current^-1、1473.23 F g^-1And 1203.68F g^-1When the specific current increases to 20A g^-1The specific capacity retention rates were 76.2% (1233.16F g)^-1）、69.8%（1029.05 F g^-1) And 63.6% (765.28F g)^-1) This shows that 2L-ZnCoS-1 obtained in example 1 realizes a higher capacity retention ratio.

FIG. 11 shows that 2L-ZnCoS-1 obtained in example 1 was at 5A g^-1Cycling performance plot at current density. As can be seen from FIG. 11, 2L-ZnCoS-1 obtained in example 1 was at 5A g^-1The specific capacitance of 82.2% is maintained after 10000 cycles under the current density of (2), because the volume change in the continuous charging and discharging process can be relieved by the gap between the double shells of the 2L-ZnCoS-1.

FIG. 12 is a graph of energy density versus power density for the 2L-ZnCoS-1 assembled asymmetric supercapacitor made in example 1. From the figure12 it can be seen that the 2L-ZnCoS-1 obtained in example 1 has a high energy density (51.76 Wh kg)^-1) And power density (8.09 kW kg)^-1). Illustrating the practical application possibility of the 2L-ZnCoS-1 assembled asymmetric supercapacitor prepared in example 1.

Claims

1. A preparation method of a double-layer hollow dodecahedron zinc-cobalt-based sulfide composite material is characterized by comprising the following specific steps:

1) preparation of 2L-ZIF-8@67

Uniformly dispersing ZIF-8@ ZIF-67 in methanol, adding zinc nitrate hexahydrate, continuously stirring, completely dissolving, adding a methanol solution of 2-methylimidazole, stirring at room temperature for more than 24 hours, centrifugally washing, and drying to obtain a ZIF-8@ ZIF-67@ ZIF-8 precipitate; dispersing the obtained precipitate in methanol, performing ultrasonic dispersion to form uniform suspension, adding cobalt nitrate hexahydrate into the suspension, continuously stirring, adding a methanol solution of 2-methylimidazole after complete dissolution, stirring for more than 24 hours at room temperature, performing centrifugal washing, and drying to obtain 2L-ZIF-8@ 67;

2) preparation of 2L-ZnCoS

Dispersing the 2L-ZIF-8@67 obtained in the step 1) into ethanol, adding thioacetamide, uniformly stirring, heating the obtained suspension at 100-200 ℃ for 60-120 min, naturally cooling to room temperature, centrifuging, washing, and drying to obtain the composite material.

2. The method of claim 1, wherein in step 1), the mass ratio of ZIF-8 to ZIF-67 in ZIF-8@ ZIF-67 is 1:1 to 3.

3. The method according to claim 1, wherein in step 1), the mass ratio of ZIF-8@ ZIF-67 to zinc nitrate hexahydrate is 1: 1-3; the mass ratio of the ZIF-8@ ZIF-67@ ZIF-8 to the cobalt nitrate hexahydrate is 1: 1-3.

4. The method of claim 1, wherein the concentration of zinc nitrate hexahydrate in step 1) is 0.1-0.2 mol L^-1And preferably 0.13 mol L^-1。

5. The method according to claim 1, wherein in step 1), the concentration of cobalt nitrate hexahydrate is 3-7 mg mL^-1Preferably 4 to 6 mg mL^-1。

6. The method of claim 1, wherein the concentration of thioacetamide in step 2) is 2-3 mg mL^-1Preferably 2.4 mg mL^-1。

7. The method of claim 1, wherein in step 2), the mass ratio of 2L-ZIF-8@67 to thioacetamide is 1: 3.

8. The method of claim 1, wherein in step 2), the resulting suspension is heated at 150 ℃ for 90 min.

9. The double-layered hollow dodecahedral zinc-cobalt-based sulfide composite material prepared by the method according to any one of claims 1 to 8.

10. Use of the double-layered hollow dodecahedral zinc cobalt-based zinc composite material prepared by the method according to any one of claims 1 to 8 as an electrode material.