Method for preparing a zif-8 wood-derived carbon-based self-supporting electrode

Abstract

The application discloses a preparation method of a ZIF-8 wood-derived carbon-based self-supporting electrode. The application comprises the following steps: wood is soaked in an acrylonitrile solution at room temperature, and Michael addition reaction occurs between cellulose in the wood and the acrylonitrile to perform cyanoization; the wood is taken out and washed clean by pure water, and then freeze-dried; the wood is soaked in a mixed solution of A solution and B solution, ZIF-8 is in-situ grown on the wood, then the wood is taken out and freeze-dried; the wood is carbonized and activated by being heated to 300 DEG C under an air atmosphere; the wood is carbonized by being heated to 900 DEG C under a nitrogen atmosphere, and a self-supporting network structure electrode is obtained; the self-supporting electrode provided in the application constructs a self-supporting network structure electrode, avoids a complicated electrode manufacturing process, eliminates the need for a conductive agent, a binder and a current collector, increases the proportion of active ingredients, has high loading capacity to increase energy density, has low tortuosity to improve the ion transmission capacity of the material.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrode preparation, in particular to a preparation method of ZIF-8 wood-derived carbon-based self-supporting electrode. BACKGROUND

[0002] The consumption of fossil fuels poses a serious threat to the environment and energy security, which has attracted public attention and promoted the research of renewable energy technologies that make high-efficiency, sustainable and environmentally friendly energy conversion, storage and chemical production and consumption possible. The development of energy conversion and storage technologies such as supercapacitors, metal-air batteries, fuel cells, water splitting and carbon dioxide reduction requires high-performance electrode materials to enhance the electrochemical processes involved. Carbon-based materials with high surface area, excellent electrical conductivity, good chemical stability and cost-effectiveness have become one of the high-performance electrode materials.

[0003] Traditional carbon-based electrode materials or catalysts are usually in the form of fine powders, requiring a tedious electrode manufacturing process, including powder dispersion, thin film casting / coating, drying, using additional binders, dispersants and conductive agents, etc. Electrochemically inactive ingredients. Improper manufacturing processes can lead to reduced active surface area, excessive dead volume, and poor interfaces that hinder electron and mass transfer, as well as increased contact resistance. In addition, manufacturing thick electrodes with high mass loading to increase energy density is a common strategy for current commercial practical applications.

[0004] Thick electrodes are limited by the following problems:

[0005] (1) Traditional thick electrodes are usually designed as stacked structures, resulting in reduced mechanical properties;

[0006] (2) Electrode dense stacking with limited ion transport path, structural layering, resulting in limited ion transport path and low electrochemical kinetic efficiency;

[0007] (3) High distortion caused by random and close arrangement of electrode components greatly hinders electrolyte penetration and ion transfer;

[0008] (4) "Dead volume" increases with increasing mass loading of electrode materials, resulting in insufficient utilization of active materials.

[0009] To solve the above problems, the present application provides a preparation method of ZIF-8 wood-derived carbon-based self-supporting electrode. SUMMARY

[0010] The application aims to provide a preparation method of a ZIF-8 wood-derived carbon-based self-supporting electrode, which is prepared by taking natural wood as a framework, adjusting a pore structure through an organic metal framework ZIF-8, and doping nitrogen elements to improve surface defects and active sites of carbon materials, so as to solve the defects in the prior art.

[0011] To solve the above technical problems, the application is realized by the following technical scheme:

[0012] The application is a preparation method of a ZIF-8 wood-derived carbon-based self-supporting electrode, which comprises the following steps.

[0013] S1: wood is soaked in an acrylonitrile solution at room temperature, and Michael addition reaction occurs between cellulose in the wood and the acrylonitrile to perform cyanation;

[0014] S2: the wood is taken out and washed clean with pure water, and then freeze-dried;

[0015] S3: the wood is soaked in a mixed solution of an A solution and a B solution, ZIF-8 is grown in situ on the wood, and then the wood is taken out and freeze-dried;

[0016] S4: the wood is carbonized and activated by being heated to 300 DEG C in an air atmosphere;

[0017] S5: the wood is carbonized by being heated to 900 DEG C in a nitrogen atmosphere, to obtain a self-supporting network structure electrode;

[0018] In the step S3, the A solution is prepared by dissolving Zn(NO3)2·6H2O in methanol, and the B solution is prepared by dissolving methyl imidazole in methanol.

[0019] Preferably, in the step S1, the soaking time is 10 h, the volume of the wood is 4*4*0.2 cm3, 72 ml of the acrylonitrile solution is used, and 2 ml of a 10% sodium hydroxide solution is added to the acrylonitrile solution.

[0020] Preferably, in the step S2, the freeze-drying time is 24 h.

[0021] Preferably, in the step S3, the A solution is prepared by dissolving 1.5 g of Zn(NO3)2·6H2O in 100 ml of methanol, and the B solution is prepared by dissolving 3.3 g of 2-methyl imidazole in 50 ml of methanol.

[0022] Preferably, in the step S3, the wood is soaked in the A solution and the B solution for 6 h, and the wood is freeze-dried for 24 h.

[0023] Preferably, in the step S4, the wood is heated at a rate of 3℃ / min, and carbonized for 2h.

[0024] Preferably, in the step S5, the wood is heated at a rate of 5℃ / min, and carbonized for 1h.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] 1. The self-supporting electrode provided in the present application constructs a self-supporting network structure electrode, avoids a complicated electrode manufacturing process, eliminates the need for conductive agents, binders and current collectors, and increases the proportion of active ingredients.

[0027] 2. The self-supporting electrode provided in the present application has high loading capacity and can increase the energy density.

[0028] 3. The self-supporting electrode provided in the present application has low tortuosity, which improves the ion transport capacity of the material.

[0029] 4. The self-supporting electrode provided in the present application has a layered porous structure, which improves the accessibility of active materials under high speed and high mass load.

[0030] 5. The self-supporting electrode provided in the present application greatly enhances active sites through nitrogen doping, enhances the chemical adsorption of ions at the electrode / electrolyte interface, and thus realizes fast kinetics. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The figure is a flowchart of the electrode preparation method in the present application;

[0032] Figure 2 The figure is a nitrogen isothermal adsorption / desorption curve during the electrode preparation process in the present application;

[0033] Figure 3 The figure is a BJH pore size distribution diagram of the electrode in the present application;

[0034] Figure 4 The figure is a CV curve of the electrode at different scanning rates in the present application;

[0035] Figure 5 The figure is a rate performance diagram of the electrode in the present application. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0037] Referring to Figures 1-5 , Figure is the preparation method of ZIF-8 wood-derived carbon-based self-supporting electrode of the application, comprising the following steps:

[0038] Wood (4×4×0.2cm3) is soaked in 72ml acrylonitrile solution (2ml 10% sodium hydroxide solution is added) at room temperature for 10 hours, washed with pure water and freeze-dried for 24 hours;

[0039] The wood pieces are soaked in a mixture of A solution (1.5g Zn(NO3)2·6H2O dissolved in 100ml methanol) and B solution (3.3g 2-methylimidazole dissolved in 50ml methanol) for 6 hours to grow ZIF-8 in situ on the wood, and then taken out and freeze-dried for 24 hours;

[0040] Carbonization and activation are carried out at an air atmosphere at a heating rate of 3℃ / min to 300℃ for 2 hours, and then carbonization is carried out at a nitrogen atmosphere at a heating rate of 5℃ / min to 900℃ for 1 hour to obtain a self-supporting network structure electrode.

[0041] The counter electrode is prepared, specifically: wood (4×4×0.2cm3) is soaked in an acrylonitrile solution at room temperature, and Michael addition reaction occurs between cellulose in the wood and acrylonitrile to cyanate, providing a nitrogen source for nitrogen-doped modification of the carbon-based material, and after freeze-drying, the wood pieces are soaked in a methanol solution of Zn(NO3)2 and 2-methylimidazole to grow imidazole acid molecular sieve framework (ZIF-8) nanoparticles in situ on the wood, and under further high-temperature carbonization, significant mass loss occurs inside the ZIF-8 nanoparticles, forming a hierarchical porous structure, while the wood framework retains the ordered porosity of the wood under the action of high-temperature activation carbonization, and rich porous structures are generated in the channel walls, this porous network structure presents a "radiation" shape, strengthening ion transport, N-doping introduces defects or disordered carbon, providing electrochemically active sites, enhancing the compatibility of the electrode, and thus obtaining higher capacitive performance.

[0042] The above is a further detailed description of the application in combination with the specific embodiments, and the specific embodiments of the application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the application belongs, without departing from the concept of the application, a number of simple deductions or substitutions can be made, which should be considered as falling within the protection scope determined by the claims submitted by the application.

Claims

1. A method for preparing a ZIF-8 wood-derived carbon-based self-supporting electrode, characterized by, The method comprises the following steps: S1: wood is soaked in acrylonitrile solution at room temperature, and Michael addition reaction between cellulose and acrylonitrile in the wood is carried out to cyanate; S2: the wood is taken out and washed with pure water, and then freeze-dried; S3: the wood is soaked in a mixed solution of A solution and B solution, and ZIF-8 is in-situ grown on the wood, and then the wood is taken out and freeze-dried; S4: the wood is carbonized and activated by being heated to 300℃ in air atmosphere; S5: the wood is carbonized by being heated to 900℃ in nitrogen atmosphere, to obtain a self-supporting network structure electrode; In the step S3, the A solution is prepared by dissolving Zn(NO3)2·6H2O in methanol, and the B solution is prepared by dissolving methyl imidazole in methanol.

2. The method for preparing the ZIF-8 wood-derived carbon-based self-supporting electrode according to claim 1, characterized in that: The soaking time in step S1 is 10h, the wood volume is 4x4x0.2cm 3 The acrylonitrile solution used is 72ml, and 2ml of 10% sodium hydroxide solution is added to the acrylonitrile solution.

3. The method for preparing the ZIF-8 wood-derived carbon-based self-supporting electrode according to claim 1, characterized in that: In the step S2, the freeze-drying time is 24h.

4. The method for preparing the ZIF-8 wood-derived carbon-based self-supporting electrode according to claim 1, characterized in that: In the step S3, the A solution is prepared by dissolving 1.5g Zn(NO3)2·6H2O in 100ml methanol, and the B solution is prepared by dissolving 3.3g 2-methyl imidazole in 50ml methanol.

5. The method of making ZIF-8 wood- derived carbon based self-supported electrode according to claim 1, wherein: In the step S3, the wood is soaked in the A solution and the B solution for 6h, and the wood is freeze-dried for 24h.

6. The method of making ZIF-8 wood- derived carbon based self-supported electrode according to claim 1, wherein: In the step S4, the wood is heated at a rate of 3℃ / min, and carbonized and activated for 2h.

7. The method for preparing the ZIF-8 wood-derived carbon-based self-supporting electrode according to claim 1, characterized in that: In the step S5, the wood is heated at a rate of 5℃ / min, and carbonized for 1h.

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