Preparation method of MoS2 / RGO composite ink

Abstract

The invention discloses a preparation method of MoS2 / RGO composite ink, which comprises the following steps: mixing a molybdenum source, a sulfur source and graphene according to a certain proportion, carrying out hydrothermal reaction, preparing composite nanosheets based on an in-situ reduction method, uniformly dispersing the composite nanosheets in a mixed solution of isopropanol and water, adding a dispersing agent such as polyvinylpyrrolidone, and preparing the MoS2 / RGO composite ink. Then ultrasonic dispersion is carried out, accumulation and agglomeration of the composite nanomaterial are reduced, the volatilization rate of the ink in the later drying process is slowed down by adding propylene glycol, and then the high-concentration and stable MoS2 / RGO composite ink is obtained. The MoS2 nanosheets are synthesized in situ on the graphene surface with high specific surface area, so that on one hand, accumulation and agglomeration of the composite material in the ink preparation process can be reduced, and on the other hand, the specific surface area of the composite material can be greatly increased, and more active sites can be provided for the composite material as an electrode material; the electrochemical performance such as specific capacity of the device is improved.

Description

Technical Field

[0001] The invention belongs to the field of electrochemical energy storage and conversion materials, and specifically relates to a preparation method and application of MoS2 / RGO composite ink. Background Art

[0002] MoS2 nanosheets have a typical two-dimensional layered stacking structure similar to graphene and S-Mo-S atoms connected by weak van der Waals forces. The two-dimensional layered structure of MoS2 makes planar devices thinner and lighter than traditional three-dimensional devices, and can achieve the unique advantage of flexibility and bendability. This two-dimensional layered structure not only gives MoS2 a higher theoretical specific surface area to achieve double-layer ion adsorption and desorption, but also allows Mo atoms to undergo Faraday pseudocapacitance reactions, ultimately obtaining a higher theoretical specific capacity. However, pseudocapacitance materials have poor conductivity, resulting in lower actual specific capacity.

[0003] By combining carbon materials such as graphene with other metal oxide or sulfide precursors to provide more active sites for their nucleation and growth, and obtaining a composite material of graphene and metal oxide or sulfide and other high pseudocapacitive materials through a one-step thermal reduction method, the composite material not only has a high specific surface area, but also has good conductivity, and can provide a conductive network for active materials with high pseudocapacitance. Through the synergistic effect of the two, devices with excellent electrochemical performance can be obtained. Composite nano inks can be used for the preparation of thin-film electronic devices. However, most nano inks currently use toxic and harmful organic solvents such as N-methylpyrrolidone, which are not only easy to pollute the environment, but also difficult to remove. The organic solvents remain in the electronic devices, posing a serious threat to human health. Summary of the invention

[0004] In order to solve the problems that composite nanomaterials are prone to agglomeration and accumulation in ink, resulting in poor electrochemical performance and stability of electronic devices, the present invention provides a method for preparing MoS2 / RGO composite ink, which has low cost, simple process, and is easy to realize industrial production. It can provide support for the application of high-concentration and high-stability composite ink in thin film device fields such as catalysis, energy storage, optoelectronics, and sensing.

[0005] The technical solution of the present invention is: a method for preparing MoS2 / RGO composite ink, comprising the following steps: S1, dissolving a molybdenum source and a sulfur source in water respectively, adding a GO solution, and stirring to obtain a precursor solution of a composite material; S2, using a precursor solution to in-situ synthesize a molybdenum disulfide and graphene composite on the graphene surface by a high-temperature hydrothermal reaction to obtain a MoS2 / RGO composite material powder; S3, dispersing the MoS2 / RGO composite material powder in a mixed solution of isopropanol and water containing a surfactant, and uniformly dispersing it by ultrasonication, then dropping a thickener to adjust the viscosity of the ink, and dispersing the solution in an ultrasonic device to obtain a MoS2 / RGO composite ink.

[0006] The mass ratio of MoS2 to RGO is 1:1-4:1.

[0007] In step S1, the molybdenum source is sodium molybdate or ammonium molybdate, and the sulfur source is thiourea or xanthate.

[0008] In step S2, the precursor solution is reacted in a high temperature and high pressure reactor, the reaction temperature is 80° C.-240° C., and the reaction time is 6 h-24 h.

[0009] In step S3, the surfactant is polyvinyl pyrrolidone or ethyl cellulose, and the mass fraction of the surfactant in the mixed solution of isopropanol and water is 0.1-2%. The surfactant is added to better stabilize the dispersion of the composite nanosheets and increase the hydrophilicity of the composite surface, thereby reducing the accumulation and agglomeration of MoS2 and RGO during the electrode preparation process.

[0010] In step S3, the volume ratio of isopropanol to water is 1:1-10:1, and the concentration of the MoS2 / RGO composite material powder dispersed in the solvent is 1 mg / ml-50 mg / ml.

[0011] In step S3, the thickener is any one or more of propylene glycol, carboxymethyl cellulose, and polyvinyl pyrrolidone, and the concentration is 0.01 ml to 3 ml of the thickener is added dropwise per 10 ml of the solution.

[0012] The ultrasonic device in step S3 is a cell crusher or a high-power ultrasonic cleaning machine, and the ultrasonic time is 0.1h-3h.

[0013] MoS2 / RGO composite ink prepared according to the preparation method.

[0014] The beneficial effects of the present invention are as follows: compared with the existing method of using toxic organic solvents such as N-methylpyrrolidone as ink solutions, the present invention selects sodium molybdate and thiourea which can be industrially produced on a large scale as raw materials, mixes them with carbon materials such as graphene, and realizes the controllable preparation of molybdenum disulfide and graphene composite materials in a high-pressure reactor through in-situ reduction technology, and disperses them in green and non-toxic solvents such as isopropanol, and realizes the controllable preparation of high-concentration and good stability ink by regulating the viscosity, surface tension and other characteristics of the solution. In terms of application, the MoS2 / RGO composite ink prepared by the present invention has the characteristics of simple process, low cost, and easy industrial production. The ink can be prepared through inkjet printing, printing, spraying and other process technologies to produce thin-film electronic devices that are widely used in catalysis, energy storage, optoelectronics, sensing, etc., providing the possibility of promoting the application in the field of flexible wearable electronic devices with designable patterns.

[0015] The present invention disperses the obtained two-dimensional nanomaterials in green and non-toxic solvents such as isopropanol, so that the alcohol solvents can be completely removed in the later device preparation process, which is more conducive to the preparation of green, environmentally friendly and highly stable composite carbon material inks for inkjet printing and printing to prepare high-performance wearable electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Scanning electron microscope images (SEM) of different ratios of MoS2 and graphene prepared in Example 1 (pure MoS2, pure graphene, and MoS2:RGO are 1:1, 2:1, 3:1, 4:1, respectively); Figure 2 Transmission electron microscopy (TEM) image of MoS2 / RGO prepared in Example 1; Figure 3 The film structure of MoS2 / RGO prepared in Example 1, as well as thermogravimetric analysis, X-ray diffraction (XRD) spectrum and Raman spectrum; Figure 4 The XPS spectrum of MoS2 / RGO prepared in Example 1; Figure 5 The MoS2 / RGO composite ink prepared in Example 1 and the flow chart; Figure 6 The planar supercapacitor device prepared on a flexible substrate using MoS2 / RGO composite ink and its morphological characterization in Example 1; Figure 7 This is a comparison chart of the performance of capacitor devices in different ratios of MoS2 / RGO in Example 1; Figure 8 Comparison of CV and GCD curves of pure RGO, pure MoS2-based devices and MoS2 / RGO composite devices; Fig. 9 This is the bendability test and stability evaluation of the capacitor device of Example 1. DETAILED DESCRIPTION

[0017] Example 1 In conjunction with the accompanying drawings, this embodiment provides a method for preparing a MoS2 / RGO composite ink, and prepares a flexible and bendable supercapacitor on a polyimide film substrate based on inkjet printing technology, and the steps are as follows: S1, four portions of 484 mg sodium molybdate and 456 mg thiourea were dissolved in 40 ml water, and then 32 ml, 16 ml, 10.7 ml and 8 ml of GO solution (10 mg / ml) were added respectively to prepare MoS2 / RGO composites with mass ratios of 1:1, 2:1, 3:1 and 4:1, respectively. After magnetic stirring for 2 h, 0.5 ml of 1 M hydrochloric acid solution was added dropwise to the mixed solution and stirred for 40 min; S2, that is, the precursor solution prepared in step 1 is sealed in a high-pressure reactor, and then transferred to a muffle furnace and maintained at 200 ° C for 24 h. After the reaction, the reaction solution is taken out, and the reaction solution is centrifuged and freeze-dried to obtain black powdered MoS2 / RGO composite nanosheets, such as Figure 1 As shown in the figure, (cf) are scanning electron microscope images of MoS2 and RGO at different ratios, which show that with the increase of the proportion of MoS2, the clustered MoS2 becomes more and more obvious. This is mainly because more molybdenum and sulfur sources are provided in the hydrothermal process, which is more conducive to the nucleation and growth on the RGO surface. More MoS2 nanosheets can be generated on the same RGO nanosheet surface. With the sharp increase of MoS2 nanosheets, more clustered MoS2 is generated. Figure 2 Shown is a transmission electron microscopy image of stably dispersed MoS2 / RGO. It can be seen that the two-dimensional lamellar MoS2 is evenly distributed on the RGO surface, and there is no obvious clustering phenomenon of MoS2 nanosheets. At the same time, elemental analysis further proves the existence of MoS2 / RGO composite materials. Figure 3 The composition analysis of composite materials with different proportions is shown in the figure. Thermogravimetric analysis and XRD analysis prove that the synthesized composite material is MoS2 / RGO composite. It can be clearly seen from the Raman spectrum that the -1 There are two characteristic peaks, which are mainly related to the E 2g and A 1g This is related to the vibration mode, which further proves the existence of MoS2 nanomaterials. Figure 4 The XPS test of the composite material is shown. The full XPS spectrum of the RGO / MoS2 composite material clearly shows the presence of Mo, S, O and C elements. The presence of O element may be caused by the sample being exposed to air and adsorbing air, which is consistent with the previous results and further proves the successful composite of RGO nanosheets and MoS2 nanosheets. S3, weigh 100 mg of MoS2 and RGO powder and disperse them in a mixed solution of isopropyl alcohol (IPA): water (volume ratio 4:1) containing 10 mg of non-ionic surfactant polyvinylpyrrolidone (PVP), and ultrasonically disperse them in an ultrasonic cleaner; add 1 ml of propylene glycol to the above solution to adjust the viscosity of the ink, and also to slow down the evaporation rate of the ink during the electrode drying process; treat the above mixed solution with a cell crusher for 2 h, on the one hand to control the sheet size of MoS2 and RGO nanosheets, on the other hand to prepare stably dispersed MoS2 and RGO ink, and finally obtain stably dispersed MoS2 / RGO ink, such as Figure 5 The figure shows the final MoS2 and RGO composite ink with high concentration and high stability and the preparation flow chart of the whole experiment, in order to further verify the applicability of the prepared ink. Figure 6 As shown in FIG. 1 , a planar supercapacitor was prepared on a flexible composite substrate based on MoS2 / RGO composite ink using inkjet printing technology, and the capacitor performance was tested, as shown in FIG. Figure 7 The figure shows the difference in electrochemical performance between devices with different ratios. The charge and discharge current density of the micro-supercapacitor with a ratio of 2:1 is much larger than that of capacitors with other ratios, and in the GCD curve, its discharge time is also significantly longer than that of other micro-supercapacitors, showing that its electrochemical performance is better than that of devices with other ratios. Figure 8 The figure shows the comparison of CV and GCD curves of pure RGO, pure MoS2-based devices and MoS2 / RGO composite devices. The charge and discharge curves of the composite MoS2 / RGO device are closer to a triangle and present a symmetrical shape, and the discharge time is also significantly increased, indicating that the electrochemical performance of the composite MoS2 / RGO device has been significantly improved. In order to further promote the practical application of the device in flexible wearables, we tested the mechanical flexibility and cycle stability of the device, such as Fig. 9 As shown, the CV of the device tested at different bending angles (0°, 45°, 90°, 135°, 180° and 360°) shows that the CV curve of the device has almost no obvious deformation, and the performance is still stable after tens of thousands of cycles. This is mainly due to the good flexibility and stability of the two-dimensional layered structure of RGO and MoS2. It also further verifies the application potential of MoS2 and RGO ink in electronic devices such as flexible supercapacitors.

[0018] Example 1: The precursor solution of MoS2, molybdenum source and sulfur source, is mixed and dispersed in an aqueous solution containing carbon materials such as graphene, and then transferred to a hydrothermal reactor. MoS2 nanosheets are prepared on the surface of RGO by an in-situ growth method under high temperature and high pressure conditions. Then, the composite RGO / MoS2 nanosheets are dispersed in a mixed solvent of isopropanol and water, and the viscosity, surface tension and other parameters of the solution are adjusted to obtain RGO / MoS2 composite ink. The implementation case verifies that MoS2 and RGO inks have good application prospects in electronic devices such as flexible capacitors.

[0019] Example 2 According to the steps of Example 1, the mass of MoS2 and RGO can be adjusted to 1:1-4:1, sodium molybdate can be replaced by ammonium molybdate, and thiourea can be replaced by xanthate. In step S2, the precursor solution is reacted in a high-temperature and high-pressure reactor, the reaction temperature is 80°C-240°C, and the reaction time is 6h-24h. In step S3, the surfactant is polyvinyl pyrrolidone or ethyl cellulose, and the mass fraction of the surfactant in the mixed solution of isopropanol and water is 0.1-2%. In step S3, the volume ratio of isopropanol to water can be adjusted to 1:1-10:1, and the concentration of MoS2 / RGO composite material powder dispersed in the solvent can be adjusted to 1mg / ml-50mg / ml. The thickener can be replaced by any one or more of propylene glycol, carboxymethyl cellulose, and polyvinyl pyrrolidone, and the concentration is 0.01ml-3ml of thickener per 10ml solution. The ultrasonic equipment can be replaced by a high-power ultrasonic cleaning machine, and the ultrasonic time is 0.1h-3h.

[0020] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A method for preparing a MoS2 / RGO composite ink, characterized in that: Here are the steps: S1, dissolving a molybdenum source and a sulfur source in water respectively, adding a GO solution, and stirring to obtain a precursor solution of a composite material; S2, using a precursor solution to in-situ synthesize a molybdenum disulfide and graphene composite on the graphene surface by a high-temperature hydrothermal reaction to obtain a MoS2 / RGO composite material powder; S3, dispersing the MoS2 / RGO composite material powder in a mixed solution of isopropanol and water containing a surfactant, and uniformly dispersing it by ultrasonication, then dropping a thickener, and dispersing the solution in an ultrasonic device to obtain a MoS2 / RGO composite ink.

2. The method for preparing the MoS2 / RGO composite ink according to claim 1, characterized in that: In step S1, the molybdenum source is sodium molybdate or ammonium molybdate, and the sulfur source is thiourea or xanthate.

3. The method for preparing the MoS2 / RGO composite ink according to claim 1, characterized in that: In step S3, the surfactant is polyvinyl pyrrolidone or ethyl cellulose.

4. The method for preparing the MoS2 / RGO composite ink according to claim 1, characterized in that: The volume ratio of isopropanol to water in step S3 is 1:1-10:

1.

5. The method for preparing the MoS2 / RGO composite ink according to claim 1, characterized in that: In step S3, the thickener is any one or more of propylene glycol, carboxymethyl cellulose, and polyvinyl pyrrolidone.

6. The method for preparing the MoS2 / RGO composite ink according to claim 1, characterized in that: The ultrasonic device in step S3 is a cell crusher or a high-power ultrasonic cleaning machine.

7. A MoS2 / RGO composite ink prepared by the preparation method as described in any one of claims 1 to 6.

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