Preparation Of Activated Carbon From Garlic-based Waste And Performance Optimization Of Supercapacitor

With more and more attention paid to energy storage and utilization,as a new type of energy storage device,supercapacitors have good development prospects.The use of biomass waste to prepare electrode materials for supercapacitors can not only utilize the natural pore structure of biomass,but also reduce the production cost of capacitors.In recent years,it has become a research hotspot.In this study,garlic cloves were used as raw materials to prepare activated carbon for supercapacitors with high specific surface area.At the same time,garlic skin was selected as the raw material,and the performance of garlic skin-based activated carbon was optimized by using the hydrochloric acid pretreatment process to effectively control the pore structure of garlic skin-based activated carbon.Using garlic cloves as raw materials and KOH as an activator,the effects of carbonization temperature,alkali-carbon ratio,and activation temperature on the pore structure of garlic-based activated carbon were studied by response surface methodology.The optimal process conditions for preparing garlic-based activated carbon were explored:the alkali-to-carbon ratio was 4:1,the carbonization temperature was 541?,and the activation temperature was 800?.The specific surface area of garlic-based activated carbon GBAC-M obtained by experiments under this condition is 3175.20 m2/g and the pore volume is 1.791 cm3/g.The pore size distribution is mainly concentrated between 0-4 nm.Supercapacitors were prepared with GBAC-M as electrode material and 6 mol/L KOH solution as electrolyte,the specific capacitance reaches 334.9 F/g at a current density of 1 A/g,and the specific capacitance retention rate is 97.03%when charged and discharged 5000 times at a current density of 5 A/g.Using garlic peel as raw material and KOH as activator,the hydrochloric acid pretreatment process was used to remove the endogenous minerals of garlic peel After demineralization,the specific surface area and mesoporous content of garlic peel-based activated carbon were significantly increased.The best experimental process for hydrochloric acid pretreatment is:after heating and stirring at 60? in a 1 mol/L hydrochloric acid solution for 3 h,the carbonization temperature is 600?.Garlic peel-based activated carbon HGAP-7 was obtained,with a specific surface area of 3325.23 m2/g,a pore volume of 1.881 cm'/g,and a mesoporous content that was significantly higher than that of the garlic peel-based activated carbon GAP without pretreatment.Using HGAP-7 as the electrode material and 6 mol/L KOH as the electrolyte,the prepared capacitor has a specific capacitance of 424.4 F/g at a current density of 1 A/g.When the current density is 50 A/g,compared with a specific capacitance of 1 A/g,the capacitance retention rate is as high as 73.8%.The specific surface area of the garlic peel-based activated carbon prepared by the hydrochloric acid pretreatment process is increased,and the mesopore content is increased.The rate performance and cycle stability of supercapacitors made with HGAP-7 as electrode materials have been significantly improved.In order to fully understand the electrochemical performance of garlic peel-based activated carbon,garlic peel-based activated carbon GAP and HGAP-7 were used as electrode materials,and polyvinyl alcohol(PVA)was selected as the raw material to prepare PVA-KOH electrolyte to assemble solid supercapacitors.The constant-current charge and discharge,cyclic voltammetry,AC impedance,and long-cycle tests were used to analyze the electrochemical performance of garlic peel-based solid supercapacitors.The specific capacitance of solid capacitors prepared with HGAP-7 as the electrode material is 230.5 F/g at a current density of 1 A/g.When the current density reaches 50 A/g,the specific capacitance can still reach 202.1 F/g.In summary,this paper has studied the preparation process,material characteristics and electrochemical properties of garlic-based activated carbon,and obtained low-cost activated carbon materials with high specific surface area and high specific capacitance.At the same time,the effect of hydrochloric acid pretreatment on the pore structure and electrochemical properties of garlic peel-based activated carbon was explored,and a simple pretreatment method for regulating the pore structure of garlic peel-based activated carbon was obtained.The electrochemical performance of garlic peel-based activated carbon in solid electrolyte and liquid electrolyte was analyzed.The research results provide theoretical basis and reference for the high value utilization of garlic-based waste and the directional regulation of the pore structure of activated carbon.