Prunus persica kernel porous carbon material, preparation method thereof and application thereof in supercapacitors

Abstract

The present application relates to the technical field of active carbon material preparation and electrochemical application, and particularly relates to a plum kernel porous carbon material and a preparation method and application thereof. The plum kernel porous carbon material is prepared from waste plum kernels through the steps of cleaning, drying, pretreatment, low-temperature carbonization, ball milling, alkali leaching, high-temperature calcination activation, carbonization and acid washing. The material has a porous layered structure, is rich in micropores and mesopores, and has excellent capacitive performance. The specific capacitance value can reach 342.0 F / g at a current density of 0.5 A / g, and the specific capacitance value can reach 335.5 F / g at a current density of 10 A / g.

Description

Technical Field

[0001] This invention relates to the fields of activated carbon biomass material preparation and electrochemical energy storage electrode material technology, specifically to a porous carbon material from plum kernels, its preparation method, and its application in supercapacitors. Background Technology

[0002] Porous carbon materials possess significant advantages such as large specific surface area, well-developed pore structure, excellent electrical conductivity, and good chemical stability, making them core functional materials in energy storage, environmental remediation, and chemical catalysis. They are currently widely used in various technological fields including supercapacitors, secondary batteries, adsorption separation, and heterogeneous catalysis. Traditional porous carbon materials are mainly prepared from fossil-based raw materials such as coal, petroleum coke, and synthetic resins. This not only results in high raw material costs and reliance on non-renewable resources but also presents problems such as high energy consumption and significant environmental burden during the preparation process, which does not align with the trend of green and low-carbon industrial development. Against this backdrop, the preparation of high-performance porous carbon materials based on agricultural and forestry biomass waste has become a research hotspot and important development direction in the field of energy storage materials.

[0003] Plum pits, a typical waste product from fruit processing, are widely sourced and produced in huge quantities. Currently, most are disposed of through indiscriminate dumping or on-site incineration, resulting in extremely low resource utilization and low product added value. This not only wastes a large amount of high-quality biomass resources but also easily leads to environmental pollution problems. Meanwhile, plum pits are rich in carbon and have a dense and stable original structure, possessing excellent carbon-forming properties. They are ideal biomass precursors for preparing high-performance porous carbon materials, with enormous potential for resource development and utilization.

[0004] Currently, the mainstream preparation processes for porous biomass carbon mainly involve direct carbonization, conventional physical activation, and chemical activation. These processes share common technical shortcomings, the core issue being the lack of refined ball milling of the biomass precursor before activation. Precursor particles that have not undergone ball milling pretreatment are large, have poor powder uniformity, and exhibit severe particle agglomeration, making it impossible to form a uniformly dispersed ultrafine carbon powder system. Furthermore, the internal structure of the material is dense. During subsequent carbonization and activation reactions, the activator cannot fully penetrate the particles, resulting in insufficient pore development, a low specific surface area of ​​the finished carbon material, and a disordered mixture of micropores, mesopores, and macropores. This poor pore size distribution significantly limits the charge adsorption and ion transport capabilities of the carbon material, ultimately leading to poor electrochemical capacitance performance.

[0005] To overcome the limitations of traditional processes in controlling pore structure, existing technologies often rely on harsh reaction conditions such as high temperatures, high activator dosages, and prolonged activation times. This not only results in cumbersome preparation steps and low activation efficiency but also easily leads to localized over-activation or under-activation, resulting in numerous structural defects and high levels of impurities in the finished carbon materials. Consequently, it is difficult to achieve efficient, controllable, and low-cost preparation of high-quality biomass porous carbon. Therefore, developing a simple, mild, fully activated, and green economical preparation technology to produce plum kernel-based porous carbon with well-developed microporous-mesoporous hierarchical pores and excellent electrochemical capacitance performance, enabling its efficient application in supercapacitor electrode materials, has significant practical and engineering application value.

[0006] Based on the shortcomings of existing technologies, this invention uses waste plum pits as the core biomass raw material to prepare functional porous carbon materials with a special microscopic multi-level pore structure, and applies them to the field of supercapacitor electrode materials. This technical solution utilizes agricultural and forestry waste fruit pits to prepare low-cost, high-performance biomass-based energy storage electrode carbon materials. This effectively solves the industry problem of low resource utilization rate of forestry and fruit waste, realizing the green, circular, and high-value utilization of agricultural and forestry waste. It also significantly reduces the preparation cost of core electrode materials for supercapacitors, overcoming the technical shortcomings of traditional fossil-based carbon materials, such as high cost, complex processes, and poor performance controllability. This has profound research value and promotional significance for the development, large-scale production, and industrial application of new green energy storage materials. Summary of the Invention

[0007] To address the shortcomings of existing biomass porous carbon preparation processes, such as coarse precursor particles, severe agglomeration, uneven activation and penetration, disordered pore development, poor electrochemical performance, harsh process conditions, cumbersome steps, numerous product impurities, and poor controllability, this invention aims to provide a method for preparing biomass porous carbon materials and their application in supercapacitors. This invention uses agricultural and forestry waste plum kernels as the sole biomass precursor and innovatively employs a pre-modification process of low-temperature pre-carbonization followed by wet ball milling. This effectively solves the core problems of dense precursor structure, uneven particle size, and insufficient activation contact area in traditional processes. Furthermore, by combining an alkaline leaching coupled with a high-temperature calcination and alkali activation synergistic preparation process, the multi-level pore structure of the carbon material is precisely controlled, resulting in biomass porous carbon materials with well-developed pores, uniform pore size, large specific surface area, and excellent electrochemical performance.

[0008] The technical solution of this invention is as follows:

[0009] A method for preparing biomass-derived porous carbon materials by coupling activation involves using agricultural waste biomass plum kernels as raw materials, and preparing the materials through steps such as washing and drying pretreatment, low-temperature carbonization, ball milling, alkaline leaching activation, acid washing to remove impurities, water washing to neutrality, and drying.

[0010] The above-mentioned method for activating and preparing biomass-derived porous carbon materials uses plum kernels as the biomass.

[0011] Furthermore, it includes the following steps:

[0012] (1) Biomass pretreatment: Take the plum kernels as biomass raw material, wash and dry them, and then crush them.

[0013] (2) Drying and crushing: Place the mixed sample from step (1) in an oven and heat it to 50-110℃ for 12-24 hours until it is completely dry. Then take it out and crush it again.

[0014] (3) Low-temperature pre-carbonization: Place the dried and crushed sample from step (2) in a tube furnace and heat it to 300-500℃ in an inert gas atmosphere for pre-carbonization. The carbonization time is 1-4 hours.

[0015] (4) Ball milling to refine particles: Place the carbon precursor obtained in step (3) in a ball mill jar and ball mill it for 12-24 hours.

[0016] (5) Alkali immersion coupled with high-temperature calcination activation: Mix the carbon precursor obtained in step (4) and the alkali activator solution evenly according to the mass ratio, and then perform immersion treatment. Place the soaked sample in an oven and heat it to 50-110℃ for 12-24 hours until it is completely dry. Place the dried sample in a tube furnace and heat it to 500-800℃ in an inert gas atmosphere for activation. The carbonization time is 1-4 hours. The product obtained is washed until neutral and dried to obtain porous carbon material;

[0017] (6) Acid washing to remove impurities: The product obtained in step (5) is acid washed to remove impurities and then washed with water until neutral and dried to obtain biomass-derived porous carbon material.

[0018] Furthermore, the method for preparing biomass porous carbon materials is characterized in that: in step (3), the pre-carbonization conditions are: under a mixture of nitrogen and hydrogen or a nitrogen atmosphere, the calcination temperature is 300-500 ℃, the heating rate is 5-10℃ / min, and the calcination time is 1-4 h.

[0019] Furthermore, the method for preparing biomass porous carbon materials is characterized in that: in step (4), the dispersion added to the ball mill jar is anhydrous ethanol, and the ball milling time is 12-24h.

[0020] Furthermore, the method for preparing biomass porous carbon materials is characterized in that: in step (5), the calcination conditions are: under a mixture of nitrogen and hydrogen or a nitrogen atmosphere, the calcination temperature is 500-800 ℃, the heating rate is 5-10 ℃ / min, and the calcination time is 1-4 h.

[0021] Further, the preparation method is characterized in that, in step (5), the alkaline activator is one or a combination of sodium hydroxide and potassium hydroxide; the mass ratio of carbon precursor to alkaline activator is 1:(1-5); and the raw material is soaked in 250mL of activating solution for 6-24h.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. By combining low-temperature pre-carbonization with fine ball milling, the particle size of the raw materials is significantly refined, agglomerates are broken up, and the activation contact area is effectively increased. This is further enhanced by a synergistic process of alkali leaching, high-temperature alkali activation, and acid washing for impurity removal, precisely controlling the multi-level pore structure. This results in a porous carbon material with a regular pore structure, high specific surface area, and excellent electrochemical performance. This process can precisely and flexibly control the pore size structure and distribution characteristics of the porous carbon material by optimizing the ratio parameters of the activator, constructing an interconnected multi-level synergistic network structure of micro, meso, and macropores. This multi-level pore structure effectively optimizes the electrolyte permeation and ion transport pathways, greatly reduces ion migration resistance, fully utilizes the synergistic energy storage advantages of the multi-level channels, and significantly improves the specific capacitance and rate energy storage performance of the material. Electrochemical characterization results demonstrate that this biomass-derived porous carbon material possesses excellent electrochemical capacitance performance. When the current density is set at 0.5 A / g, the specific capacitance of the material is in the range of 200~350 F / g.

[0024] 3. The alkali dosage in this process is controllable and the equipment corrosion is minimal, effectively reducing the risk of equipment corrosion. The experimental raw material is plum pit waste, which is widely available and inexpensive. Furthermore, the preparation process optimizes the particle size of the raw material, eliminating the need for additional sieving. The overall process is green and environmentally friendly. Attached Figure Description

[0025] Figure 1 This is a SEM image of the biomass-derived porous carbon material prepared in Example 1 of the present invention;

[0026] Figure 2 This is the GCD diagram of the biomass-derived porous carbon material obtained in Example 1 of the present invention at 0.5 A / g;

[0027] Figure 3 The image shows the GCD of the biomass-derived porous carbon material prepared in Example 1 of this invention at 10 A / g.

[0028] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] A method for preparing biomass-derived porous carbon materials through coupling activation includes the following steps:

[0032] (1) Biomass pretreatment: Take the plum kernels as biomass raw material, wash and dry them, and then crush them.

[0033] (2) Drying and crushing: Place the mixed sample from step (1) in an oven and heat it to 60°C for 12 hours until it is completely dry. Then take it out and crush it again.

[0034] (3) Low-temperature pre-carbonization: The dried and crushed sample from step (2) is placed in a tube furnace and pre-carbonized at 300°C in an inert gas atmosphere for 3 hours.

[0035] (4) Ball milling to refine particles: The carbon precursor obtained in step (3) is placed in a ball mill jar and ball milled for 12 hours.

[0036] (5) Alkali immersion coupled with high-temperature calcination activation: Mix the carbon precursor obtained in step (4) and the alkali activator solution evenly according to the mass ratio, and then perform immersion treatment. Place the soaked sample in an oven and heat it to 60℃ for 12 hours until it is completely dry. Place the dried sample in a tube furnace and heat it to 600℃ in an inert gas atmosphere for activation. The carbonization time is 3 hours. The product obtained is washed until neutral and dried to obtain porous carbon material;

[0037] (6) Acid washing to remove impurities: After acid washing to remove impurities, the product obtained in step (5) is washed with water until neutral and then dried to obtain biomass-derived porous carbon material.

[0038] To investigate the pore structure of the carbon material in Example 1, scanning electron microscopy (SEM) was performed on the sample. The test results are as follows: Figure 1 As shown, the carbon material in Example 1 has a rich pore structure.

[0039] To demonstrate that the carbon material in this embodiment possesses good specific capacitance and good rate performance, constant current charge-discharge tests were conducted on the sample at different current densities. The test results are as follows: Figure 2 and Figure 3As shown, when the current density is 0.5 A / g, the specific capacitance of the sample reaches 342.0 F / g. At a current density of 10 A / g, the specific capacitance still reaches 335.5 F / g. The data shows that Example 1 has good specific capacitance and rate performance.

[0040] Comparative Example 1

[0041] In this comparative example, all preparation steps and parameters are the same as in Example 1, except that ball milling is not performed in step (4).

[0042] Comparing Example 1 and Comparative Example 1, the results are as follows:

[0043]

[0044] Low-temperature pre-carbonization followed by wet ball milling refines the powder, breaking down large aggregates of carbon from the fruit kernels, resulting in finer particles with more uniform distribution. The specific surface area of ​​the powder is significantly increased, allowing the activator to fully penetrate the interior of the particles and resulting in more complete pore development. This forms interconnected micropore-mesopore multi-level channels, enabling faster electrolyte ion transport and lower migration resistance. The particles exhibit good dispersibility, reducing dead volume caused by agglomeration and significantly increasing the number of effective energy storage sites.

[0045] Example 2

[0046] In this embodiment, the preparation steps and parameters are the same as in Example 1, except that in step (1), distiller's grains are used as the biomass raw material:

[0047] Comparative Example 2

[0048] In this comparative example, all preparation steps and parameters are the same as in Example 2, except that ball milling is not performed in step (4).

[0049] Comparing Example 2 and Comparative Example 2, the results are as follows:

[0050]

[0051] Ball milling is a universally applicable process: whether it is plum pits or distillers' grains biomass, ball milling can refine particles and increase the activation contact area, making the pore formation of alkaline leaching + high temperature activation more uniform and the pore size distribution more regular, thereby improving specific capacitance and conductivity stability.

[0052] Example 3

[0053] In this embodiment, all preparation steps and parameters are the same as in Example 1. The difference is that in step (6), the alkaline immersion coupled with high-temperature calcination activation is not used, but instead, a single solid alkali is used for high-temperature calcination activation.

[0054] Compared with Example 1, the results are as follows:

[0055]

[0056] The alkaline leaching coupling process outperforms single high-temperature calcination activation in terms of specific capacitance and specific surface area. First, liquid-phase alkaline leaching adsorption: the activator is pre-adsorbed uniformly onto the surface and internal pores of the carbon precursor, avoiding localized agglomeration and uneven activation at high temperatures; the alkaline leaching pretreatment pre-etches preliminary pores, followed by secondary pore expansion through high-temperature calcination, resulting in hierarchical pore formation and a more developed pore hierarchy; the activation reaction is gentler and more uniform, avoiding localized over-ablation or under-activation, resulting in fewer defects in the carbon material and a more complete conductive network; the synergistic effect of the multi-level pore structure preserves the micropore storage capacity while accelerating ion diffusion through mesopores, significantly improving rate performance.

[0057] Example 4

[0058] In this embodiment, all preparation steps and parameters are the same as in Example 2. The difference is that in step (6), instead of using an alkaline solution for impregnation coupled with high-temperature calcination activation, an alkaline high-temperature calcination activation is used.

[0059] Compared with Example 2, the results are as follows

[0060]

[0061] Liquid-phase impregnation allows the activator to achieve molecular-level contact with the biomass carbon precursor, resulting in a much higher pore-forming efficiency than direct solid-state mixing and calcination, making it suitable for a variety of biomass raw materials.

[0062] Example 5

[0063] In this embodiment, all preparation steps and parameters are the same as in Example 1, except that the proportions of pre-activated precursor, sodium hydroxide, and potassium hydroxide are different.

[0064]

[0065] Note: Examples 5-1 and 5-2 use sodium hydroxide as an activator, while Examples 5-3 and 5-4 use potassium hydroxide as an activator.

[0066] Example 5 and Summary of Example Data

[0067]

[0068] KOH has a stronger etching and pore-forming ability than NaOH, making it easier to construct rich microporous and mesoporous structures with a larger specific surface area. The optimal alkali-to-carbon ratio is 1:4: this ensures a moderate amount of activator, sufficient pore formation, and no excessive corrosion of the carbon skeleton. A ratio that is too high (1:5) can easily cause excessive etching and structural collapse of the carbon skeleton, which in turn reduces conductivity and specific capacitance. A moderate amount of alkali results in fewer impurities and higher coulombic efficiency and cycle retention.

[0069] Example 6

[0070] In this embodiment, all preparation steps and parameters are the same as in Example 1. The difference is that the pre-activation and high-temperature synergistic activation parameters in step (1) are different.

[0071] Specifically as follows:

[0072]

[0073] The performance data for Example 6 is shown in the table below:

[0074]

[0075] Pre-activation at 550℃ + high-temperature activation at 700℃ yields the best overall performance; too low a temperature results in insufficient pore formation, while too high a temperature leads to framework collapse. A moderate pre-carbonization temperature ensures sufficient biomass pyrolysis and the formation of a stable carbon precursor without premature sintering and pore closure. A suitable high-temperature activation temperature allows for controllable activation and etching rates, precisely generating a micropore-mesopore synergistic network. Too low a temperature results in insufficient activation, fewer pores, lower specific surface area, and poorer specific capacitance. Too high a temperature causes thermal shrinkage of the carbon material framework, pore collapse, and a reduction in effective energy storage sites, ultimately leading to a decrease in performance.

[0076] To demonstrate that the carbon material in this embodiment possesses good specific capacitance and good rate performance, constant current charge-discharge tests were conducted on the sample at different current densities. The test results are as follows: Figure 2 and Figure 3 As shown, when the current density is 0.5 A / g, the specific capacitance of the material reaches 342.0 F / g, and at 10 A / g, the specific capacitance value reaches 335.5 F / g. The sample exhibits excellent specific capacitance and good rate storage characteristics, fully demonstrating that the porous carbon material of plum kernel prepared in this invention has excellent electrochemical application potential.

[0077] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing a biomass porous carbon material, characterized in that, The product is obtained through a series of processes including raw material pretreatment, drying and crushing, low-temperature pre-carbonization, ball milling and refining, alkaline leaching coupled with high-temperature calcination and activation, acid washing and impurity removal, and water washing and drying.

2. The method for preparing biomass porous carbon material according to claim 1, characterized in that, The biomass raw material used is plum kernels, which are activated by alkaline leaching and then ball-milled to refine the powder before activation.

3. The method for preparing biomass porous carbon materials as described in claim 1, characterized in that, Includes the following steps: (1) Biomass pretreatment: Take the plum kernels as biomass raw material, wash and dry them, and then crush them. (2) Drying and crushing: Place the mixed sample from step (1) in an oven and heat it to 50-110℃ for 12-24 hours until it is completely dry. Then take it out and crush it again. (3) Low-temperature pre-carbonization: Place the dried and crushed sample from step (2) in a tube furnace and heat it to 300-500℃ in an inert gas atmosphere for pre-carbonization. The carbonization time is 1-4 hours. (4) Ball milling to refine particles: Place the carbon precursor obtained in step (3) in a ball mill jar and ball mill it for 12-24 hours. (5) Alkali immersion coupled with high temperature activation: Mix the carbon precursor from step (4) with the alkaline activator solution according to the mass ratio and immerse for 6-24 hours; after immersion, place in an oven at 50-110℃ and dry for 12-24 hours; after drying, transfer to a tube furnace and activate at 500-800℃ in an inert gas atmosphere for 1-4 hours. (6) Acid washing to remove impurities: After acid washing to remove impurities, the product obtained in step (5) is washed with water until neutral and then dried to obtain biomass-derived porous carbon material.

4. The preparation method according to claim 3, characterized in that: In step (3), the pre-carbonization conditions are: under a mixture of nitrogen and hydrogen or a nitrogen atmosphere, the calcination temperature is 300-500 ℃, the heating rate is 5-10 ℃ / min, and the calcination time is 1-4 h.

5. The preparation method according to claim 3, characterized in that: Step (4) The ball milling medium is anhydrous ethanol, and the entire process is wet ball milling to avoid particle agglomeration.

6. The preparation method according to claim 3, characterized in that: In step (5), the calcination conditions are: the high-temperature activation inert atmosphere is pure nitrogen or a nitrogen-hydrogen mixture, the heating rate is 5-10℃ / min, and the high-temperature activation holding time is 1-4h.

7. The preparation method according to claim 3, characterized in that, Step (5) The alkaline activator is one or a combination of sodium hydroxide and potassium hydroxide; the mass ratio of carbon precursor to alkaline activator is 1:(1-5); prepare a 250mL activation solution for constant temperature soaking.

8. Application of a porous carbon material from plum kernels in supercapacitor electrodes.

Images