Preparation Of Porous Carbons Derived From Kapok Fiber And Willow Catkin For Electrochemical Energy Storage And CO₂ Capture

Porous carbons obtain high specific surface area and developed pore structure,which makes them have important application prospect in electrochemical energy storage and gas absorption.Biomass materials as raw materials for the preparation of porous carbons,possess the advantages of sustainability,wide source,causing people's attention.Chemical treatments(H2O2,NaOH,NaOCl et al)to biomass materials surface can improve the hydrophilicity,modify surface microstructure,change surface chemical property and composition.For these reasons,the performance of porous carbons derived from these treated biomass may be effected,however the related research is less.(1)We report a novel synthetic method to prepare the porous carbons via H2O2 and EDTA-K pre-treatment of kapok fiber,then carbonization and KOH-activation.Compared with porous carbons derived from non-treated kapok fiber,the better electrochemical performance and CO2 adsorption capacity of as-obtained samples from pre-treated kapok fiber are ascribed to its unique microflake structure with abundant micropores and rich O-heteroatom.In a three-electrode system,the KFOE-4K sample derived from pre-treated kapok fiber with the KOH/C of 4 respectively exhibits the unprecedented specific capacitance of 645 and 322 F g-1 at 0.1 and 40 A/g.While the optimal sample displays a ultra-high specific capacitance of 365 F g-1(237 F cm-3),258 F g-1(168 F cm-3)at 0.1 A g-1,50 A g-1,respectively in the two-electrode system with KOH aqueous electrolyte.Moreover,the sample with the KOH/C of 3 from pre-treated kapok fiber exhibits the high CO2 uptake of 6.32 mmol g-1(27.81 wt.%).(2)We prepared the willow catkin derived porous carbons via the same method as above.The results show that pre-treatment can enhance the proportion of surface O-1 heteroatom,increase the specific surface area and mesopores contents of samples.Thus,the electrochemical performance of samples in supercapacitors is improved.The CKOE-4K sample derived from pre-treated willow catkin with the KOH/C of 4 exhibits the highest specific surface area(3509 m2 g-1)and O contents(6.38 at%).In a three-electrode system,the CKOE-4K respectively exhibits 341 and 232 F g-1 at 0.1 and 10 A/g.While the optimal sample displays a ultra-high specific capacitance of 246 F g-,198 F g-1 at 0.1 A g-1 and 50 A g-1,respectively in the two-electrode system with KOH aqueous electrolyte.In the ionic liquid electrolyte(EMIM BF4),the capacitance of 204 and 153 F g-1 at 0.5 and 30 A g-1 respectively,the excellent energy density of 72 Wh kg-1 at power density of 399 W kg-1 are obtained,which can light the diode for 3.5 min.