Investigation Of Heteroatom Doped Biomass Porous Carbon Materials Applied In Supercapacitors

The environmental problems caused by the consumption of fossil energy are becoming more and more serious,and the large-scale use will cause more serious energy shortages.Therefore,it is imminent to find clean and renewable energy an alternative energy source,which is of great significance for sustainable development in the future.Traditional renewable energy sources such as solar energy and wind energy have a lot of limitations in terms of use conditions.Emerging energy storage devices such as supercapacitors are favored by researchers because of their advantages such as good reversibility,excellent stability,and long cycle life.It has been used in various energy storage fields,such as providing starting power and stable voltage in the start-stop systems,and providing backup power and peak power for key automotive applications.With the increasing demand for energy,the low energy density of supercapacitors has become an obstacle to further development.Biomass porous carbon has attracted extensive attention due to its wide source,low price,high specific surface area,and easy structure control.In this paper,corn stover andβ-cyclodextrin were used as raw materials and doped with heteroatoms,and hybrid porous carbon materials with excellent electrochemical properties were successfully prepared.The specific research contents are as follows:（1）Corn stalk powder,ammonium chloride and zinc chloride were used as carbon source,nitrogen source and activated agent,respectively.First,the corn stalk powder is hydrothermally pretreated to obtain spherical carbon,which is then mixed with ammonium chloride and zinc chloride and activated at high temperature to prepare nitrogen-doped biomass porous carbon materials.By adjusting the ratio of zinc chloride and ammonium chloride to carbon source,a carbon material N_xPC_ywith a hierarchical porous structure was prepared,and the changes in the morphology,structure and electrochemical performance of porous carbon were explored.The specific surface area is as high as 1123.5 m²g^-1,and it exhibits a high specific capacitance(321.5 F g^-1at 0.5 A g^-1);by constructing a symmetric supercapacitor,when the power density is 500 W kg^-1,the energy density can reach 25.7 Wh kg^-1.Moreover,the capacitance retention rate is 93%after 10,000 cycles at 20 A g^-1.（2）Direct preparation of boron-nitrogen co-doped porous carbon materials by one-step carbonization method using clean and environmentally friendlyβ-cyclodextrin as precursor,and boric acid and urea as the boron and nitrogen sources,respectively.By adjusting the ratio of boric acid and urea to cyclodextrin and carbonization temperature,the optimized experimental conditions were determined,and the boron-nitrogen co-doped porous carbon BN₄CD₈₀₀was successfully prepared.The characterization results show that BN₄CD₈₀₀has an interconnected pore structure and a specific surface area as high as 2005.5 m²g^-1.In the three-electrode system,it exhibits high specific capacitance(626.5 F g^-1at 0.5 A g^-1).The symmetrical supercapacitor can still maintain a high specific capacitance(155 F g^-1at 0.5 A g^-1),and the energy density can reach 21.8 Wh kg^-1when the power density is 500 W kg^-1.The capacitance retention is 96%after 10,000 cycles at 20 A g^-1with excellent cycling stability.