Preparation Of Activated Carbon By Carbon Dioxide Activation And Its Application In Supercapacitor

With the increasing use of fossil fuels,the pursuit of renewable,clean and environmentally friendly energy is becoming increasingly intense in the world.Lithium ion battery has been widely used in various mobile devices,but its safety,cycle life and low power density have limited its development.And the supercapacitor can effectively make up for some shortcomings of lithium ion battery,with high safety,almost no capacity loss after10,000 cycles,and large power density and many other advantages.Biomass is a kind of renewable resource that exists in large quantities in nature and is often used to prepare carbon materials.The porous carbon material can be used as electrode material in supercapacitors.There are abundant biomass materials in hainan.In this paper,coconut shell carbonization materials were selected as raw materials to prepare activated carbon and applied in supercapacitors.Considering the cost of industrial manufacturing,the activated carbon mainly containing micropores was prepared by using CO₂ as activator and coconut shell carbonized material as carbon source.The activation temperature was 900℃,the holding time was 3 h,the CO₂ flow was 200 ml·min^-1.The specific surface area of the activated carbon was1245.26 m²·g^-1,and the specific capacitance was up to 162 F·g^-1.The pore size is the key factor that affects the capacitance performance.When analyzing the pore size distribution of activated carbon,it was found that the non-closure of absorption and desorption isotherms would lead to artificial peaks on the pore size distribution curve.The forced closure of the isotherm hysteresis line at 0.4 P/P₀ caused by the tensile strength effect will produce an artificial peak near 3 nm.Therefore,adsorption branch is recommended to analyze the pore size distribution of activated carbon,while desorption branch can be used to analyze the pore structure and morphology.