Preparation of nitrogen-doped porous carbons with ultra-highsurface areas for high-performance supercapacitors

N-doped porous carbons with ultra-high surface area was prepared by simple grinding and carbonizationusing sucrose as the carbon source,urea as the nitrogen source,and potassium oxalate as the activator.The effectsof potassium oxalate and urea at different temperatures on the specific surface area,nitrogen content,and capacitiveperformance of carbons were investigated.The results showed that the specific surface area of KC-800preparedusing only potassium oxalate as an activation agent was1114m(2)center dot g(-1),while the specific surface area of KNC-800prepared using both potassium oxalate and urea was as high as3033m(2)center dot g(-1).In a three-electrode system,the specificcapacitance of KNC-800was405F center dot g(-1) at the current density of0.5A center dot g(-1),while the specific capacitance of KC-800was only248F center dot g(-1),indicating that the synergistic effect of potassium oxalate and urea can significantly improve thespecific surface area and capacitive performance.The capacitance contribution analysis showed that both the electri-cal double-layer capacitance and pseudocapacitance values of KNC-800were higher than those of KC-800.KNC-800maintained an initial specific capacitance of98.3% after10000cycles at0.5A center dot g(-1),demonstrating excellentcycling performance