Preparation Of Modified Straw-based Activated Carbon Electrode Material And Analysis For Its Properties

China is a big agricultural country and tons of straw are remained after harvesting seeds which is valuable biomass resources with green,low carbon,sustainable supply and other incomparable advantages and characteristics.These biomass can be converted into electrical stored and used in daily life.However,the efficient storage and release of electrical energy is a difficult problem to overcome.Supercapacitor is a new type of energy storage device between traditional capacitor and rechargeable battery.It is receiving more and more attention because of its higher energy and power density,faster charge and discharge time and longer life.At present,in the research of the electrode material of supercapacitors,straw-based carbon material has low specific surface area and single pore structure resulting in low specific capacitance and poor electrochemical performance.Therefore,in order to meet the needs of practical applications,it is imperative to modify and optimize straw-based carbon materials as supercapacitor electrode material.In this study,acid mine wastewater?AMD?is used to pretreat the straw,Then use carbonization and activation method to prepare a variety of modified activated carbon,and examine its electrochemical performance as supercapacitor electrode material.Meanwhile manganese dioxide ore were mixed with the straw to prepare the electrode material.The main conclusions are as follows:?1?As the p H of AMD increased from 2 to 5,the specific surface area and specific capacitance of the activated carbon obtained increases first and then decreases.When the p H of AMD is 4,the specific surface area of straw-based activated carbon prepared under this condition is the largest,reaching 1703 m²g^-1,the pore volume reaches 0.905 cm³g^-1,and has hierarchical porous structure including micropores/mesoporous and macropores.At the same time,the specific capacitance also reaches the maximum.When the current density is 1 A g^-1,the specific capacitance in the aqueous electrolyte is as high as 262.0 F g^-1.After 5000 cycles of constant current charge/discharge at current density of 10 A g^-1,the specific capacitance retention is still as high as 93.92%.?2?As the carbonization temperature increases,the specific surface area and specific capacitance of activated carbon modified by manganese dioxide ore increases first and then decreases.The total pore volume increases first,then decreases and then increases.When the carbonization temperature is 400?,the specific surface area of straw-based activated carbon prepared under this condition is the largest,reaching1559 m²g^-1,the pore volume is 1.001 cm³g^-1.The ratio of mesopores to micropores is1.42,which indicates that activated carbon has multilevel pore structure.The specific capacitance of the sample also reaches maximum when the carbonization temperature is 400?.The specific capacitance in aqueous electrolyte is 224.5 F g^-1when the current density is 1 A g^-1.After 5000 cycles of constant current charge/discharge at current density of 10 A g^-1,the specific capacitance retention is 93.92%.