CN114974935A - Preparation method and application of conjugated molecular phthalocyanine modified MnO2 electrode material - Google Patents

Abstract

The invention discloses a preparation method and application of a conjugated molecular phthalocyanine modified MnO ₂ electrode material, and belongs to the field of material preparation. The invention adjusts the electronic properties of MnO ₂ through simple phthalocyanine modification, thereby improving the electrochemical performance and stability of the MnO ₂ electrode material.

Description

Preparation method and application of conjugated molecular phthalocyanine modified MnO2 electrode material

technical field

The invention belongs to the field of electrode material preparation, and mainly relates to a preparation method of a supercapacitor electrode material.

Background technique

Limited sources of fossil fuels, as well as growing population and technological development, have confronted humanity with energy problems. Energy storage technology is an important means to meet the large-scale access of renewable energy. Supercapacitors are considered as potential renewable energy storage devices due to their excellent rate performance and long-term cycling stability.

Supercapacitors are a new type of energy storage device between batteries and traditional electrostatic capacitors. Compared with traditional electrostatic capacitors, supercapacitors have outstanding advantages such as large capacity, high power density, fast charging and discharging speed, and long cycle life, and are widely used in many fields such as electronics, aerospace, and automobiles. However, the low energy density of supercapacitors limits their large-scale applications. Therefore, it is of great significance to develop supercapacitors with high energy density and serve as power sources for practical devices.

In the components of supercapacitors, the electrode material is an important limiting factor to further increase the energy density. Among them, _MnO2 , as a variable valence transition metal oxide, has attracted extensive research attention due to its high theoretical capacitance, low production cost, and environmental friendliness. However, due to its inherent semiconducting properties, problems such as poor electrical conductivity and slow Na ⁺ diffusion kinetics limit its practical application.

To solve the above problems, phthalocyanine-modified _MnO2 electrode materials are currently prepared to improve the charge storage capacity. The performance of _MnO2 -based supercapacitors is strongly influenced by the electronic structure of the electrode material. However, the inherent semiconducting characteristics of _MnO2 make it have poor electron/ion transport ability. Phthalocyanine molecule, as a large conjugated structure molecule, contains abundant and freely mobile π electrons. By modifying phthalocyanine molecules on the surface of _MnO2 material to improve its electrical conductivity, the internal electron transfer of _MnO2 is promoted. But so far, few reports have been reported on chemically modifying conjugated structures onto _MnO surfaces and applying them in the field of energy storage.

SUMMARY OF THE INVENTION

The primary purpose of the present invention is to prepare an electrode material for supercapacitors. Using phthalocyanine to modify MnO ₂ electrode material to improve the stability and electrochemical performance of manganese dioxide.

For realizing the above-mentioned technical purpose, the technical scheme adopted in the present invention is as follows:

The supercapacitor electrode material of the present invention comprises the following synthesis steps:

Step 1: at room temperature, dissolve the metal manganese salt and the phthalocyanine molecular monomer (Pc) in a mixed solvent (distilled water and ethanol in a volume ratio of 1:1) and stir until the mixture is uniform to form solution A;

Step 2: Prepare 30% aqueous hydrogen peroxide solution and aqueous sodium hydroxide solution, and stir evenly;

Step 3: Under stirring, pour the sodium hydroxide solution into solution A, adjust the pH to 9-12, and then add the hydrogen peroxide solution, and observe that the solution quickly turns dark brown, and is accompanied by a large number of bubbles and Precipitation was formed, sonicated for 1 hour, followed by stirring for 5 hours, washed with deionized water and ethanol solution, filtered the obtained product, dried in an oven, and ground to obtain a phthalocyanine-modified MnO ₂ electrode material, denoted as MnO ₂ -Pc.

In step (1), the metal manganese salt is selected from Mn(NO ₃ ) ₂ ;

In step (3), every 1.3-1.5 g of Mn(NO ₃ ) ₂ corresponds to 4 mL of 30% hydrogen peroxide.

The molar ratio of Pc and Mn(NO ₃ ) ₂ is (0.005-0.05):1, preferably 0.01:1.

The material obtained in the present invention is used in supercapacitors.

The electrode material prepared by the method of the present invention has larger capacitance and smaller resistance. The _MnO2 electrode material modified by phthalocyanine molecules has high electronic conductivity, which accelerates the transfer of electrons and improves the problem of low conductivity of _MnO2 as a semiconductor material.

The MnO ₂ -Pc electrode material prepared by the method of the present invention has high reversible capacity, which is 310F·g ^-1 when the current density is 1A·g ^-1 , and has excellent cycle stability, at 1A·g ^-1 After 10000 cycles, the capacity retention rate is 84.3%, and it also has excellent rate performance (211.6F·g ^-1 at 20A·g ^-1 current density).

Description of drawings

Figure 1 is the SEM images of the prepared materials MnO ₂ and MnO ₂ -Pc with different magnification ratios; (a)-(b) are the SEM images of the MnO ₂ material, (c)-(d) are the SEM images of the MnO ₂ -Pc material picture.

Figure 2 is the TEM image, HRTEM image and SAED image of the prepared material MnO ₂ and MnO ₂ -Pc; (a)-(d) are the TEM image, HRTEM image and SAED image of the MnO ₂ material, (e)-(h ) is the TEM image, HRTEM image and SAED image of MnO ₂ -Pc material.

Fig. 3 is the XRD comparison of the prepared material MnO ₂ and MnO ₂ -Pc;

Figure 4 is the XPS comparison diagram of the obtained materials MnO ₂ and MnO ₂ -Pc; (a) and (b) are the XPS N1s diagrams of the Pc molecule and MnO ₂ -Pc, respectively.

Fig. 5 is the constant current test result and cyclic voltammetry test result of the material MnO ₂ and MnO ₂ -Pc;

Figure 6 shows the four-probe test results of MnO ₂ and MnO ₂ -Pc.

Detailed ways

The present invention will be further described below in conjunction with the examples, but the present invention is not limited to the following examples.

Example 1

At room temperature, 1.43g Mn(NO ₃ ) ₂ and 0.04g C ₃₂ H ₁₈ N ₈ ie Pc (the molar ratio of Pc and Mn(NO ₃ ) ₂ is 0.01:1) were dissolved in a mixed solvent (distilled water and ethanol as 1:1), stir until the mixture is evenly mixed to form a 40ml solution, in the case of magnetic stirring, dropwise add sodium hydroxide solution (preferably 1mol/L sodium hydroxide aqueous solution), adjust the pH to 10, and then slowly add 4ml of 30% of hydrogen peroxide solution. The solution was observed to quickly turn dark brown with a lot of bubble generation and precipitation, sonicated for 1 hour, followed by stirring for 5 hours, washed with deionized water, ethanol solution, filtered, and dried in an oven, ground A phthalocyanine-modified MnO ₂ electrode material was obtained, denoted as MnO ₂ -Pc.

Example 2 (comparative example)

At room temperature, 1.43g Mn(NO ₃ ) ₂ was dissolved in a mixed solvent (distilled water and ethanol 1:1) and stirred until the mixture was uniform to form a 40ml solution. Under magnetic stirring, sodium hydroxide solution was added dropwise to adjust the pH. to 10, then slowly add 4 ml of 30% hydrogen peroxide solution. It was observed that the solution quickly turned dark brown, and accompanied by a large number of bubbles and precipitations, sonicated for 1 hour, then stirred for 5 hours, washed with deionized water, ethanol solution, filtered, and oven dried to obtain the product by grinding. MnO ₂ electrode material.

Fig. 1 is the SEM images of the prepared materials MnO ₂ and MnO ₂ -Pc with different magnification ratios. (a)-(b) are the SEM images of the MnO ₂ material, and (c)-(d) are the SEM images of the MnO ₂ -Pc material.

FIG. 2 is the TEM image, HRTEM image and SAED image of the prepared materials MnO ₂ and MnO ₂ -Pc. (a)-(d) are TEM images, HRTEM images and SAED images of MnO ₂ material, (e)-(h) are TEM images, HRTEM images and SAED images of MnO ₂ -Pc material. It can be seen from the SEM and TEM images that the prepared material is an ultra-thin layered structure material.

Figure 3 shows the XRD comparison of the prepared materials MnO ₂ and MnO ₂ -Pc; it can be seen from the XRD pattern that the introduction of phthalocyanine during the preparation process does not change the crystal structure of MnO ₂ .

Figure 4 is the XPS comparison diagram of the obtained material MnO ₂ and MnO ₂ -Pc; from the XPS Pc N1s diagram, it can be seen that phthalocyanine and MnO ₂ chemically interact to form N-Mn chemical bonds, and the peaks can be seen from the XPS Mn 2p diagram The position shifts to lower binding energies, which proves that the electron-gaining process occurs in the Mn atom.

FIG. 5 shows the galvanostatic charge-discharge test results and the cyclic voltammetry test results of the materials MnO ₂ and MnO ₂ -Pc. Electrochemical measurements were carried out in a three-electrode system with platinum sheets and Ag/AgCl as counter and reference electrodes, respectively, in a 1 mol/L Na ₂ SO ₄ aqueous solution. Galvanostatic charge-discharge (GCD) tests and cyclic voltammetry (CV) tests were performed within a potential window of 0-1 V. Figure 5(a) is the GCD curves of MnO ₂ and MnO ₂ -Pc at a current density of 1Ag ^-1 , showing that the MnO ₂ -Pc electrode has a high specific capacitance of 310F g ^-1 , while the MnO ₂ electrode only has a high specific capacitance of 182.8 Low specific capacitance of F g ^-1 . Figure 5(b) is the CV diagram of MnO ₂ and MnO ₂ -Pc at 20 mV s ^-1 , showing that MnO ₂ -Pc has better electrochemical performance.

Figure 6 shows the four-probe test results of MnO ₂ and MnO ₂ -Pc. The results showed that MnO ₂ -Pc exhibited higher electrical conductivity than MnO ₂ at 1 MPa, 2 MPa and 3 MPa (1 MPa: 0.56818 mS m ^-1 vs 0.04274 mS m ^-1 ; 2 MPa: 0.74627 mS m ^{- 1} vs 0.05714 mS m ^-1 ; 3MPa: 0.8547mSm ^-1 vs 0.07463mSm ^-1 ). It shows that the phthalocyanine modification leads to an increase in the electron transport rate.

The above descriptions are only embodiments of the present invention, and common knowledge such as well-known specific structures and characteristics in the solution are not described too much here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation of the present invention. effect and the applicability of the patent.

Claims (6)

1. a preparation method of conjugated molecular phthalocyanine modified _MnO electrode material, is characterized in that, comprises the following steps: Step 1: at room temperature, the metal manganese salt and the phthalocyanine monomer are dissolved in a mixed solvent and stirred to form a solution A. The mixed solvent is distilled water and the volume ratio of ethanol is 1:1; Step 2: Prepare 30% aqueous hydrogen peroxide solution and aqueous sodium hydroxide solution, and stir evenly; Step 3: Under stirring, pour the sodium hydroxide solution into solution A, adjust the pH to 9-12, and then add the hydrogen peroxide solution, and observe that the solution quickly turns dark brown, and is accompanied by a large number of bubbles and Precipitation was formed, sonicated for 1 hour, followed by stirring for 5 hours, washed with deionized water and ethanol solution, filtered the obtained product, dried in an oven, and ground to obtain a phthalocyanine-modified MnO ₂ electrode material, denoted as MnO ₂ -Pc. 2 . The method for preparing a conjugated molecular phthalocyanine-modified MnO ₂ electrode material according to claim 1 , wherein each 1.3-1.5 g of Mn(NO ₃ ) ₂ corresponds to 4 mL of 30% hydrogen peroxide. 3. according to the preparation method of a kind of conjugated molecular phthalocyanine modified _MnO electrode material according to claim 1, it is characterized in that, the mol ratio of Pc, Mn(NO ₃ ) ₂ is (0.005-0.05): 1, 0.01:1 is preferred. 4. A conjugated molecular phthalocyanine modified MnO ₂ electrode material prepared by the method according to any one of claims 1-3. 5. A conjugated molecular phthalocyanine-modified MnO ₂ electrode material prepared according to the method of any one of claims 1-3, wherein the phthalocyanine induces an increase in the intrinsic conductivity of MnO ₂ . 6. Application of a conjugated molecular phthalocyanine-modified MnO ₂ electrode material prepared according to the method of any one of claims 1-3, for supercapacitors.

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