Preparation method of ZIF-8 wood-derived carbon-based self-supporting electrode

Abstract

The invention discloses a preparation method of a ZIF-8 wood derived carbon-based self-supporting electrode. The method comprises the following steps that wood is soaked in an acrylonitrile solution at the room temperature, and cellulose in the wood and acrylonitrile are subjected to a Michael addition reaction for cyanidation; the wood is taken out and washed clean with purified water, and then freeze drying is conducted; the wood is soaked in a mixed solution of the solution A and the solution B, ZIF-8 grows on the wood in situ, and then the wood is taken out and freeze-dried; the wood is heated to 300 DEG C in the air atmosphere, carbonized and activated; heating the wood to 900 DEG C in a nitrogen atmosphere, and carbonizing to obtain a self-supporting network structure electrode; according to the self-supporting electrode and the self-supporting network structure electrode provided by the invention, the tedious electrode manufacturing process is avoided, the requirements on a conductive agent, an adhesive and a current collecting agent are eliminated, the proportion of active components is increased, the self-supporting electrode has high loading capacity, energy density can be increased, the self-supporting electrode has low torsion resistance, and the ion transmission capacity of the material is improved.

Description

Technical Field

[0001] The invention relates to the field of electrode preparation, in particular to a method for preparing a ZIF-8 wood-derived carbon-based self-supporting electrode. Background Art

[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, which enable efficient, sustainable and environmentally friendly energy conversion, storage and chemical production and consumption. The development of energy conversion and storage technologies including 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 have high surface area, excellent conductivity, good chemical stability and cost-effectiveness, and have become one of the high-performance electrode materials.

[0003] Conventional carbon-based electrode materials or catalysts are usually in fine powder form, requiring cumbersome electrode manufacturing processes, including powder dispersion, thin film casting / coating, drying, and the use of additional electrochemically inactive ingredients such as binders, dispersants, and conductive agents. Improper manufacturing processes may 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 issues:

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

[0006] (2) Densely packed electrodes and structural stratification with restricted ion transport paths lead to restricted ion transport paths and low electrochemical kinetic efficiency;

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

[0008] (4) The “dead volume” increases with the mass loading of electrode materials, resulting in insufficient utilization of active materials.

[0009] In response to the above problems, this application document proposes a method for preparing ZIF-8 wood-derived carbon-based self-supporting electrodes, which can effectively solve the above problems. Summary of the invention

[0010] The purpose of the present invention is to provide a method for preparing a ZIF-8 wood-derived carbon-based self-supporting electrode, using natural wood as a frame, adjusting the pore structure through an organic metal framework ZIF-8, doping nitrogen elements to increase the surface defects and active sites of the carbon material, and preparing an integrated self-supporting network structure electrode without a binder, a conductive agent, a dispersant and a current collector, so as to solve the defects in the prior art.

[0011] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0012] The present invention is a method for preparing a ZIF-8 wood-derived carbon-based self-supporting electrode, comprising the following steps:

[0013] S1: The wood is immersed in an acrylonitrile solution at room temperature, and the cellulose in the wood undergoes a Michael addition reaction with acrylonitrile to cause cyanidation;

[0014] S2: After the wood is taken out and rinsed with pure water, it is freeze-dried;

[0015] S3: The wood is immersed in a mixture of solution A and solution B to grow ZIF-8 in situ on the wood, and then the wood is removed and freeze-dried;

[0016] S4: heating the wood to 300°C in an air atmosphere for carbonization and activation;

[0017] S5: heating the wood to 900°C in a nitrogen atmosphere for carbonization to obtain a self-supporting network structure electrode;

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

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

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

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

[0022] Preferably, in step S3, the immersion time of the wood in solution A and solution B is 6 hours, and the freeze-drying time of the wood is 24 hours.

[0023] Preferably, in step S4, the wood temperature is raised at a rate of 3°C / min and carbonization activation is performed for 2 hours.

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

[0025] Compared with the prior art, the present invention has the following beneficial effects:

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

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

[0028] 3. The self-supporting electrode provided by the present invention has low distortion and improves the ion transmission capacity of the material.

[0029] 4. The self-supporting electrode provided by the present invention has a layered porous structure, which improves the accessibility of active materials at high rates and high mass loads.

[0030] 5. The self-supporting electrode provided in the present invention has nitrogen doping which greatly enhances the active sites and the chemical adsorption of ions at the electrode / electrolyte interface, thereby achieving fast kinetics. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the process of preparing the electrode of the present invention;

[0032] Figure 2 Schematic diagram of nitrogen isothermal adsorption-desorption curve during electrode preparation in the present invention;

[0033] Figure 3 Schematic diagram of BJH pore size distribution of the electrode in the present invention;

[0034] Figure 4 Schematic diagram of CV curves of the electrode at different scanning rates in the present invention;

[0035] Figure 5 Schematic diagram of the electrode rate performance in the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] See also Figure 1-5 , the figure shows a method for preparing a ZIF-8 wood-derived carbon-based self-supporting electrode according to the present invention, comprising the following steps;

[0038] The wood (4×4×0.2 cm3) was immersed in 72 ml of acrylonitrile solution (added with 2 ml of 10% sodium hydroxide solution by mass) at room temperature for 10 h, rinsed with pure water, and freeze-dried for 24 h;

[0039] The wood chips were immersed in a mixture of solution A (1.5 g Zn(NO3)2·6H2O dissolved in 100 ml methanol) and solution B (3.3 g 2-methylimidazole dissolved in 50 ml methanol) for 6 h, ZIF-8 was grown in situ on the wood, and then freeze-dried for 24 h;

[0040] In an air atmosphere, the temperature was raised to 300°C at a rate of 3°C / min and carbonized for 2 hours; in a nitrogen atmosphere, the temperature was raised to 900°C at a rate of 5°C / min and carbonized for 1 hour to obtain a self-supporting network structure electrode.

[0041] For electrode preparation, specifically: wood (4×4×0.2cm3) was immersed in acrylonitrile solution at room temperature, and cyanidation was carried out through Michael addition reaction between cellulose and acrylonitrile in the wood, providing a nitrogen source for nitrogen doping modification of carbon-based materials. After freeze-drying, the wood chips were immersed in a methanol solution of Zn(NO3)2 and 2-methylimidazole, and imidazolic acid molecular sieve framework (ZIF-8) nanoparticles were in situ grown on the wood. Under further high-temperature carbonization, significant mass loss occurred inside the ZIF-8 nanoparticles, forming a hierarchical porous structure. At the same time, under the action of high-temperature activated carbonization, the wood framework retained the ordered porosity of the wood and produced a rich porous structure in the channel wall. This "radial" porous network structure enhanced the ion transmission process. N doping introduced defective or disordered carbon, provided electrochemically active sites, and enhanced the compatibility of the electrode, thereby obtaining higher capacitance performance.

[0042] The above content is a further detailed description of the present invention in combination with specific implementation methods. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the scope of protection determined by the claims submitted for the present invention.

Claims

1. A method for preparing a ZIF-8 wood-derived carbon-based self-supporting electrode, characterized in that: The method comprises the following steps: S1: The wood is immersed in an acrylonitrile solution at room temperature, and the cellulose in the wood undergoes a Michael addition reaction with acrylonitrile to cause cyanidation; S2: After the wood is taken out and rinsed with pure water, it is freeze-dried; S3: The wood is immersed in a mixture of solution A and solution B to grow ZIF-8 in situ on the wood, and then the wood is taken out and freeze-dried; S4: heating the wood to 300°C in an air atmosphere for carbonization and activation; S5: heating the wood to 900°C in a nitrogen atmosphere for carbonization to obtain a self-supporting network structure electrode; In step S3, solution A is prepared by dissolving Zn(NO3)2·6H2O in methanol, and solution B is prepared by dissolving methylimidazole in methanol.

2. The method for preparing the ZIF-8 wood-derived carbon-based self-supporting electrode according to claim 1, characterized in that: In the step S1, the soaking time is 10 hours, the volume of the wood is 4×4×0.2 cm3, 72 ml of acrylonitrile solution is used, and 2 ml of a sodium hydroxide solution with a mass fraction of 10% 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 step S2, the freeze-drying time is 24 hours.

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

5. The method for preparing the ZIF-8 wood-derived carbon-based self-supporting electrode according to claim 1, characterized in that: In step S3, the immersion time of the wood in solution A and solution B is 6 hours, and the freeze-drying time of the wood is 24 hours.

6. The method for preparing the ZIF-8 wood-derived carbon-based self-supporting electrode according to claim 1, characterized in that: In step S4, the wood temperature is raised at a rate of 3°C / min, and the carbonization activation is performed for 2 hours.

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

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