Preparation Of Peanut Shell Based Activated Carbon Electrode Materials And Their Electrochemical Performance

In this paper,low-cost and regenerable peanut shells are used as precursors,and a biomass activated carbon electrode material with high electrochemical performance is prepared by chemical activation method,and then through CO₂ activation,hydrothermal carbonization,chemical pretreatment,and doping heteroatom to improve its electrochemical performance.The preparation of peanut shells as electrode materials for supercapacitors can not only reduce the production cost of supercapacitors,but also avoid the waste of agricultural and forestry wastes and environmental pollution,and is one of the effective ways to realize the utilization of biomass resources.The specific research work of this article is as follows:?1?Using peanut shells as precursors and metal salt?ZnCl₂ and FeCl₃?as activators,a method for preparing activated carbon electrode materials by one-step activation is designed,and the effects of different activators and impregnation ratios on the microstructure and electrochemical performance of activated carbon are studied.The structure and characteristics of the obtained activated carbon are characterized by SEM,HRTEM,BET,XRD,Raman and FT-IR.The BET results show that the prepared activated carbon material has a high specific surface area and a large number of micropores.The maximum specific surface area can reach 1481.59m²/g.A large number of micropores are mainly formed by the etching of the carbon skeleton by ZnCl₂ and FeCl₃.XRD patterns and Raman spectra indicate that all samples are amorphous carbon with a certain graphite crystal structure.In addition,FT-IR analysis find that the surface of the activated carbon material has a large number of oxygen-containing functional groups,these functional groups are beneficial to improve the electrochemical performance of carbon materials.The electrochemical performance of the activated carbon material is characterized by electrochemical tests.It is found that when the mass ratio of activator to biomass is2:1,the activated carbon material has the best electrochemical properties,and ZN-PSAC-2 exhibits more excellent electrochemical performance than FE-PSAC-2.The obtained ZN-PSAC-2 sample has the specific capacitance of 216.5 F/g at the current density of 0.5 A/g and has excellent cycle stability.?2?On the basis of ZnCl₂ activation,a method is proposed to prepare peanut shell-based porous graphite carbon with high electrochemical performance by chemically pretreating peanut shells through NH₄OH,HNO₃ and H₂SO₄,coupled with hydrothermal carbonization and ZnCl₂/CO₂ activation.The results show that,compared with HNO₃ and H₂SO₄,NH₄OH pretreatment has the best modification effect on activated carbon.When the activation temperature is 700°C,thanks to its high surface area and good pore size distribution,NHAC-700 exhibits the best electrochemical performance.On this basis,the effect of activation temperature on the modification effect of NH₄OH is studied.When the activation temperature is increased to 800°C,the porosity and electrochemical performance of the biomass carbon treated with NH₄OH are further improved.The prepared NHAC-800 has a porous structure rich in micropores and mesopores and its surface area reaches 2129.5m²/g.In the three-electrode system,when the current density is 0.5 A/g,the specific capacitance of the NHAC-800 electrode reaches 266.1 F/g.In the two-electrode system,the maximum energy density of a symmetrical capacitor composed of NHAC-800 is 32.08 Wh/kg.In addition,NHAC-800 symmetrical capacitor also shows excellent cycle stability,its specific capacitance retention rate after 5000 cycles is 93.76%.?3?On the basis of hydrothermal carbonization and NH₄OH pretreatment,a method for preparing peanut shell-based nitrogen-doped porous carbon with high electrochemical performance by ZnCl₂/CO₂ activated coupling melamine nitriding is proposed.The prepared activated carbon has a large surface area and a hierarchical porous structure composed of abundant micropores and mesopores.By doping with nitrogen,the nitrogen-containing functional groups on the surface of the activated carbon are effectively increased.These nitrogen-containing functional groups can produce pseudocapacitors while improve the conductivity of the activated carbon,which plays an important role in improving the electrochemical performance of the activated carbon.This experiment also explores the effect of doping ratio on the electrochemical performance of activated carbon.It is found that excessive doping ratio would damage the pore structure of activated carbon and reduce the electrochemical performance of activated carbon electrode materials.The best sample for this study?NHAC-2?is obtained with a mass ratio of melamine to activated carbon of 2:1,and the surface area of the material reaches 2014.6 m²/g.In the three-electrode system,NHAC-2 can provide a high specific capacitance of 310.6 F/g at a current density of 0.5 A/g.At the same time,in the two-electrode system,the specific capacitance of the symmetric supercapacitor assembled by NHAC-2 at a current density of 0.5 A/g is 300.6 F/g.In addition,NHAC-2 also has excellent rate performance and good cycle stability.