A pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array and its preparation method and application
By growing CuCo2S4 nanosheets on a conductive substrate and constructing a Co-MOF core-shell structure to form a pn heterojunction, the stacking problem of two-dimensional MOF materials was solved and the electrochemical performance of supercapacitors was improved.
Patent Information
- Application Number
- CN202310757300.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-13
- Publication Date
- 2025-09-26
- Estimated Expiration
- 2043-06-13
AI Technical Summary
Two-dimensional metal-organic framework (MOF) materials are prone to accumulation and agglomeration in supercapacitors, resulting in poor conductivity and electrochemical stability, affecting their electron transfer efficiency and energy storage capacity.
CuCo2S4 nanosheet arrays were grown on a conductive substrate, and a Co-MOF core-shell structure was constructed on it to form a pn heterojunction. The pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet arrays were prepared by hydrothermal method and room temperature in situ growth method.
It improves the conductivity and electron transfer efficiency of the material, enhances the energy storage capacity, achieves high specific capacitance and good rate performance, and is suitable for supercapacitor electrode materials.
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Figure CN116813927B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the interdisciplinary field of nanomaterial preparation methods and electrochemical applications, and specifically relates to a pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array and its preparation method and application. Background Art
[0002] Supercapacitors are a new type of green energy storage device that bridges the gap between traditional capacitors and rechargeable batteries. Their advantages include long lifespan, high power density, wide operating temperature range, relatively low cost, and eco-friendliness, making them promising applications in various portable electronic devices and new energy vehicles. Electrode materials are a key factor influencing supercapacitor performance, making the development and identification of promising electrode materials particularly important.
[0003] Two-dimensional metal-organic framework (MOF) materials have a large surface area and fully exposed active sites, making them ideal electrode materials. However, two-dimensional MOFs are prone to stacking and agglomeration, which reduces the electron transfer efficiency and makes the material's conductivity and electrochemical stability worse. In order to solve the limitations of two-dimensional MOF materials, an effective method is to directly grow MOF arrays on a conductive substrate (such as nickel foam) and combine them with other electrochemically active materials (such as transition metal sulfides) to form a core-shell material with a pn heterojunction. First, the complementary and synergistic effects between different components will enhance the energy storage capacity; second, the construction of a pn heterojunction will change the built-in electric field of the material, causing the redistribution of electrons, thereby improving the electron transfer efficiency, stabilizing the structure, and further improving the electrochemical performance of the MOF material. Summary of the Invention
[0004] To address the aforementioned technical issues, the present invention utilizes a simple, low-cost preparation method to fabricate a pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array. First, growing Co-MOF on a porous CuCo2S4 nanosheet array effectively addresses issues such as poor conductivity and easy accumulation. Second, the two-dimensional Co-MOF with its large surface area, ordered pores, and ultrathin thickness can address issues such as the sluggish kinetics of CuCo2S4 during redox reactions. Finally, the formation of the pn heterojunction helps regulate electron flow, enhancing the synergistic effect and thus improving the material's energy storage capacity. Therefore, the pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array material is widely applicable to the field of supercapacitors and is an ideal electrode material.
[0005] The present invention provides a method for preparing a pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array material, comprising the following steps:
[0006] (1) After dissolving cobalt salt, copper salt and 2-methylimidazole in deionized water, the cleaned nickel foam was added and allowed to react at room temperature for 2 h. After washing with distilled water, the mixture was dried in a blast drying oven to obtain a Cu-Co-ZIF precursor.
[0007] (2) placing the Cu-Co-ZIF precursor in a sulfur source solution for sulfurization reaction to obtain a porous CuCo2S4 nanosheet array;
[0008] (3) Dispersing cobalt salt and terephthalic acid in a mixed solvent of N,N-dimethylformamide, deionized water and anhydrous ethanol to form a uniform reaction solution, immersing the porous CuCo2S4 nanosheet array prepared in step (2) in the above solution, and obtaining a pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array after hydrothermal reaction.
[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 copper salt is not limited, including copper chloride, copper nitrate, copper sulfate, etc., but copper nitrate trihydrate is most preferred.
[0010] In the step (1), the molar ratio of cobalt nitrate hexahydrate, copper nitrate trihydrate and 2-methylimidazole is (1-3): (1-2): (7-10), but the optimal ratio is 2:1:8.
[0011] In the step (1), the volume of deionized water used is 50-100 mL, but most preferably 80 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 100-120° C. and the reaction time is 3-7 hours, but the most preferred reaction time is 4 hours at 120° C.
[0014] In step (3), the type of cobalt salt is not limited, including cobalt nitrate, cobalt chloride, cobalt acetate, etc., but cobalt chloride trihydrate is most preferred.
[0015] In the step (3), the hydrothermal temperature is 100-160°C, but most preferably 120°C.
[0016] In the step (3), the hydrothermal reaction time is 6 to 18 hours, but most preferably 9 hours.
[0017] In summary, the pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array of the present invention has the following beneficial effects:
[0018] (1) The raw material cost required to prepare CuCo2S4 is low, and the synthesis process is simple. It can be synthesized only through room temperature in-situ growth method and hydrothermal method. In addition, the CuCo2S4 material itself has good conductivity, rich redox reactions, strong electrochemical activity, and its internal porous structure can well adapt to the volume expansion problem during the reaction. The composite of CuCo2S4 with high specific capacitance and large surface area Co-MOF ultra-thin nanosheet materials can increase the redox reaction sites, shorten the ion diffusion path, and inhibit the accumulation and agglomeration of Co-MOF. The pn heterostructure is constructed to obtain a built-in electric field, which redistributes electrons at the heterogeneous interface, improves the electron transfer rate, and fully enhances the synergistic effect of different components. Therefore, it is possible to achieve improvements in the material in many aspects such as specific capacitance and rate performance.
[0019] (2) The pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array prepared by the present invention exhibited high specific capacitance and rate performance in electrochemical tests. Cyclic voltammetry curves and constant current charge-discharge curves were measured using a CHI 660E electrochemical workstation. The cyclic voltammetry curve tests were carried out at scan rates of 5, 10, 20, 30, 50, and 100 mV / s, with a voltage range of -0.1 to 0.6 V. The constant current charge-discharge tests were carried out at current densities of 1, 2, 3, 5, and 10 A / g, with a voltage range of 0 to 0.4 V. At a current density of 1 A / g, the electrode material had a high specific capacitance of 2388.9 F / g. Even at a current density of 10 A / g, the electrode material had a specific capacitance of 1193.3 F / g, indicating good rate performance.
[0020] (3) The preparation method of the present invention is simple and effective, and the construction of the pn heterostructure electrode material demonstrated can be simply extended to construct heterojunction electrode materials of other metal sulfides or MOFs for energy storage devices. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is a scanning electron microscope image of the Cu-Co-ZIF precursor prepared in step (1) of Example 1 of the present invention;
[0022] Figure 2 This is a scanning electron microscope image of the CuCo2S4 nanosheet array prepared in step (2) of Example 1 of the present invention;
[0023] Figure 3 This is a scanning electron microscope image of the pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array prepared in step (3) of Example 1 of the present invention;
[0024] Figure 4The X-ray diffraction pattern of the pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array prepared in step (3) of Example 1 of the present invention is compared with the standard card;
[0025] Figure 5 Mott-Schottky curve of the pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array prepared in step (3) of Example 1 of the present invention;
[0026] Figure 6 The electrochemical performance diagram of the pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array prepared in step (3) of Example 1 of the present invention as an electrode material in a 2M KOH electrolyte solution. The left figure is a cyclic voltammetry curve at different scan rates, and the right figure is a charge-discharge curve at different current densities;
[0027] Figure 7 The specific capacitance of the porous CuCo2S4 nanosheet array prepared in step (2) of Example 1 of the present invention and the pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array prepared in step (3) as electrode materials in 2M KOH electrolyte solution. DETAILED DESCRIPTION
[0028] The preferred embodiments of the present invention are described in further detail below with reference to the accompanying drawings and examples.
[0029] Example 1
[0030] A method for preparing a pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array comprises the following steps:
[0031] (1) 0.388 g of cobalt nitrate hexahydrate, 0.162 g of copper nitrate trihydrate, and 1.313 g of 2-methylimidazole were dissolved in 80 mL of deionized water to obtain a reaction solution. The nickel foam was placed in the reaction solution and reacted at room temperature for 2 h. The nickel foam was washed with ethanol and distilled water and then dried in a forced air drying oven to obtain a Cu-Co-ZIF precursor. The scanning electron microscope image of the precursor is shown in FIG. Figure 1 As shown, the nanosheet morphology is smooth and has a certain thickness;
[0032] (2) The Cu-Co-ZIF precursor was placed in a thioacetamide solution and reacted at 120°C for 4 hours to obtain a porous CuCo2S4 nanosheet array. The scanning electron microscope image is shown in FIG. Figure 2 As shown, it presents a rough surface and porous nanosheet morphology;
[0033] (3) 0.237 g of cobalt chloride hexahydrate, 0.166 g of terephthalic acid and 25 mL of N, N-dimethylformamide were mixed and stirred to form a uniform reaction solution, and 2.5 mL of deionized water and 2.5 mL of anhydrous ethanol were slowly added dropwise to the mixed solution and stirred for 30 minutes. The porous CuCo2S4 nanosheet array prepared in step (2) was then immersed in the reaction solution and subjected to hydrothermal reaction at 120 ° C for 9 hours to obtain a pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array, the scanning electron microscope image of which is shown in FIG. Figure 3 As shown, it presents a core-shell morphology of nanosheets encapsulating nanosheets.
[0034] The X-ray diffraction pattern of CuCo2S4@Co-MOF prepared in the above steps is as follows: Figure 4 As shown; the diffraction peaks are all attributed to CuCo2S4 (JCPDS No.42-1450) and Co-MOF.
[0035] The CuCo2S4@Co-MOF array prepared above was subjected to Mott-Schottky curve test. Figure 5 As shown in the figure, the curve of the CuCo2S4@Co-MOF array exhibits an inverted "V" shape, with both positive and negative slopes, proving that the material is a pn-type semiconductor. This result shows that CuCo2S4@Co-MOF is a composite material with a pn heterojunction.
[0036] The CuCo2S4@Co-MOF prepared above was used as a supercapacitor electrode material, and its electrochemical performance was tested in 2M KOH electrolyte solution. Figure 6 The left figure shows the cyclic voltammetry curves at different scan rates, and the right figure shows the charge and discharge curves at different current densities.
[0037] The CuCo2S4@Co-MOF and CuCo2S4 prepared above were used as supercapacitor electrode materials, and their specific capacitance at different current densities was tested in 2M KOH electrolyte solution. Figure 7 As shown, CuCo2S4@Co-MOF and CuCo2S4 have specific capacitances of 2388.9 F / g and 1037.8 F / g at 1 A / g, respectively, indicating that the electrochemical performance is greatly improved by assembling Co-MOF ultrathin nanosheets on CuCo2S4 nanosheet arrays to construct a pn heterojunction.
[0038] Example 2
[0039] (1) 0.437 g of cobalt nitrate hexahydrate, 0.121 g of copper nitrate trihydrate, and 1.313 g of 2-methylimidazole were dissolved in 80 mL of deionized water to obtain a reaction solution. Nickel foam was placed in the reaction solution and reacted at room temperature for 4 hours. The mixture was washed with ethanol and distilled water and then dried in a forced air drying oven to obtain a Cu-Co-ZIF precursor.
[0040] (2) The Cu-Co-ZIF precursor was placed in a thioacetamide solution and reacted at 120 °C for 4 h to obtain a porous CuCo2S4 nanosheet array;
[0041] (3) 0.237 g of cobalt chloride hexahydrate, 0.166 g of terephthalic acid and 35 mL of N,N-dimethylformamide were mixed and stirred to form a uniform reaction solution. 2.5 mL of deionized water and 2.5 mL of anhydrous ethanol were slowly added dropwise to the mixed solution and stirred for 30 minutes. The CuCo2S4 nanosheet array prepared above was then immersed in the reaction solution and subjected to hydrothermal reaction at 125 °C for 12 hours to obtain a pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array.
[0042] The prepared pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array 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 has a high specific capacitance of 2010.4F / g at 1A / g.
[0043] Example 3
[0044] (1) 0.291 g of cobalt nitrate hexahydrate, 0.242 g of copper nitrate trihydrate, and 1.313 g of 2-methylimidazole were dissolved in 80 mL of deionized water to obtain a reaction solution. Nickel foam was placed in the reaction solution and reacted at room temperature for 4 hours. The mixture was washed with ethanol and distilled water and then dried in a forced air drying oven to obtain a Cu-Co-ZIF precursor.
[0045] (2) The Cu-Co-ZIF precursor was placed in a thioacetamide solution and reacted at 120 °C for 4 h to obtain a porous CuCo2S4 nanosheet array;
[0046] (3) 0.237 g of cobalt chloride hexahydrate, 0.166 g of terephthalic acid and 25 mL of N,N-dimethylformamide were mixed and stirred to form a uniform reaction solution. 2.5 mL of deionized water and 2.5 mL of anhydrous ethanol were slowly added dropwise to the mixed solution and stirred for 30 minutes. The CuCo2S4 nanosheet array prepared above was then immersed in the reaction solution and subjected to hydrothermal reaction at 120 °C for 12 hours to obtain a pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array.
[0047] The prepared pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array 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 has a high specific capacitance of 1980.7F / g at 1A / g.
[0048] Example 4
[0049] (1) 0.388 g of cobalt nitrate hexahydrate, 0.162 g of copper nitrate trihydrate, and 1.313 g of 2-methylimidazole were dissolved in 80 mL of deionized water to obtain a reaction solution. Nickel foam was placed in the reaction solution and reacted at room temperature for 4 hours. The mixture was washed with ethanol and distilled water and then dried in a forced air drying oven to obtain a Cu-Co-ZIF precursor.
[0050] (2) The Cu-Co-ZIF precursor was placed in a thioacetamide solution and reacted at 100 °C for 4 h to obtain a porous CuCo2S4 nanosheet array;
[0051] (3) 0.237 g of cobalt chloride hexahydrate, 0.166 g of terephthalic acid and 35 mL of N,N-dimethylformamide were mixed and stirred to form a uniform reaction solution. 2.5 mL of deionized water and 2.5 mL of anhydrous ethanol were slowly added dropwise to the mixed solution and stirred for 30 minutes. The CuCo2S4 nanosheet array prepared above was then immersed in the reaction solution and subjected to hydrothermal reaction at 125 °C for 12 hours to obtain a pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array.
[0052] The prepared pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array 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 has a high specific capacitance of 2000.2F / g at 1A / g.
[0053] Example 5
[0054] (1) 0.388 g of cobalt nitrate hexahydrate, 0.162 g of copper nitrate trihydrate, and 1.313 g of 2-methylimidazole were dissolved in 80 mL of deionized water to obtain a reaction solution. Nickel foam was placed in the reaction solution and reacted at room temperature for 4 hours. The mixture was washed with ethanol and distilled water and then dried in a forced air drying oven to obtain a Cu-Co-ZIF precursor.
[0055] (2) The Cu-Co-ZIF precursor was placed in a thioacetamide solution and reacted at 160 °C for 4 h to obtain a porous CuCo2S4 nanosheet array;
[0056] (3) 0.237 g of cobalt chloride hexahydrate, 0.166 g of terephthalic acid and 35 mL of N,N-dimethylformamide were mixed and stirred to form a uniform reaction solution. 2.5 mL of deionized water and 2.5 mL of anhydrous ethanol were slowly added dropwise to the mixed solution and stirred for 30 minutes. The CuCo2S4 nanosheet array prepared above was then immersed in the reaction solution and subjected to hydrothermal reaction at 120°C for 9 hours to obtain a pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array.
[0057] The prepared pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array 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 has a high specific capacitance of 1874.8F / g at 1A / g.
[0058] The embodiments described above are detailed descriptions of the technical solutions of the present invention and should be understood as specific implementation measures of the present invention. They are not intended 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 a pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array, characterized in that: The preparation method comprises the following steps: (1) Dissolve 0.388 g of cobalt nitrate hexahydrate, 0.162 g of copper nitrate trihydrate, and 1.313 g of 2-methylimidazole in 80 mL of deionized water to obtain a reaction solution. Place the cleaned nickel foam into the reaction solution, react at room temperature for 2 h, wash with distilled water, and then dry in a forced air drying oven to obtain a Cu-Co-ZIF precursor. (2) The Cu-Co-ZIF precursor was placed in a thioacetamide solution and subjected to a sulfurization reaction at 120 °C for 4 h to obtain a porous CuCo2S4 nanosheet array; (3) 0.237 g of cobalt chloride hexahydrate, 0.166 g of terephthalic acid and 25 mL of N,N-dimethylformamide were mixed and stirred to form a uniform reaction solution. Finally, 2.5 mL of deionized water and 2.5 mL of anhydrous ethanol were slowly added dropwise to the mixed solution and stirred for 30 minutes. The porous CuCo2S4 nanosheet array prepared in step (2) was immersed in the solution and subjected to hydrothermal reaction at 120°C for 9 hours to obtain a pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array.
2. The pn heterojunction CuCo2S4@Co-MOF core-shell nanosheet array prepared by the preparation method according to claim 1 is characterized in that The core-shell nanosheet array is composed of n-type semiconductor Co-MOF nanosheets embedded on the surface of p-type semiconductor CuCo2S4 porous nanosheets.
3. The p prepared by the preparation method according to claim 1 - Application of heterojunction CuCo2S4@Co-MOF core-shell nanosheet arrays as supercapacitor electrode materials.