Preparation And Electrochemical Performance Of Scallion-based Activated Carbon

Biomass as a renewable resource has broad prospects for research and development in alternative fuels,carbon-based materials and natural products.In recent years,research on the use of biomass carbon materials as electrode materials for supercapacitors has become a research focus.In this paper,the scallion was used as raw material to prepare activated carbon electrode material for supercapacitor,and the pore structure and electrochemical performance of activated carbon were improved by different treatment processes,and the preparation method of high performance activated carbon was obtained and an effective scheme for the pore structure directional control of activated carbon was provided.The activated carbon ASAC(Acid treatment Scallion-based Activated Carbon)was prepared by using two-step acid washing step with scallion as the raw material and KOH as the activator.When the impregnation ratio is 5,the highest specific surface area is 3289.76 m2·g-1 and the specific pore volume is 1.89 cm3·g-1.Under this condition,the mesopores(2.0-3.5 nm)increased significantly,and the micropores(0.5-0.7 nm)were still the main pores.In the two-electrode system of 6 M KOH electrolyte,the specific capacitance reaches 381.51 F·g-1 at a current density of 1.0 A·g-1,after 5,000 cycles,the capacitance retention rate reached 92.8%.The activated carbon ESAC(Ethanol pretreatment Scallion-based Activated Carbon)was prepared by introducing the ethanol pretreatment process to increase the number of mesopores in the activated carbon material,and the best material properties were obtained at the impregnation ratio of 5.The specific surface area reached 3375.45 m2·g-1,and the specific pore volume reached 2.21 cm3·g-1,the number of mesopores is significantly increased(2.0～3.5 nm)under this condition,and the micropores are still the main pore structure(0.5-0.7 nm).The highest specific surface area of ESAC at a current density of 1.0 A·g-1,the specific capacitance reached 399.29 F·g-1,after 5,000 cycles,the capacitance retention rate reached 97.2%.Activated carbon PSAC(Potassium ferrate activation Scallion-based Activated Carbon)was prepared by using K2FeO4 instead of KOH as activator.When the impregnation ratio was 4,the specific surface area of activated carbon reached a maximum of 2355.88 m2 g-1,and the specific pore volume reached 1.558 cm3·g-1.When K2FeO4 is used as the activator,the number of mesopores(2-4 nm)is further increased and the pore morphology is changed from a slit-type pore structure to a circular pore structure,and the micropores are still distributed in the range of 0.5-0.7 nm.The activated carbon was tested under the condition of a two-electrode system.At a current density of 1.0 A·g-1 the specific capacitance reached 343.14 F g’.After 5000 cycles,the capacitance retention rate was as high as 98.9%with little attenuation.In summary,this paper explores the effects of different treatment processes on the pore structure of onion-based activated carbon,material properties and electrochemical properties.The effects of the number of mesopores on the rate performance and cycle performance of activated carbon and the effect of different activators on the pore morphology were explored.The research results provide a theoretical basis and reference for screening porous carbon materials and synthetic processes.