Heteroatom self-doped graphitic carbon materials from Sargassum thunbergii with improved supercapacitance performance

It is well-known that high specific surface area and improved pore structure is significantly desired for the application of supercapacitor based on biomass-based activated carbon.Herein,Sargassum thunbergii was selected as carbon precursor.Then,a simple and environmentally friendly method was designed to synthesize heteroatom self-doped porous carbon materials via synchronous activation and graphitization by using K_(2)FeO_(4).Our results demonstrated that activation temperature plays an important role in porous structure,morphology,and degree of graphitization,thus affecting the performance of supercapacitance.Sargassum thunbergii-based graphitized porous carbons STGPC-2 sample(calcination temperature at 700℃)has a large specific surface area(1641.98 m^(2)g^(-1)),pore volume(0.91 cm^(3)g^(-1)),high microporosity(Vmicro=0.62 cm^(3)g1,more than 68%),and a certain degree of graphitization.In three-electrode system,The STGPC-2 electrode exhibited a high specific capacitance of 325.5 F g^(-1)at 0.5 A g^(-1)and displays high rate capability(248 F g^(-1)at 10 A g^(-1)in 6 M KOH electrolyte).The symmetric STGPC-2 supercapacitor exhibits energy density as high as 21.3 Wh kg^(-1)(at a power density of 450 W kg^(-1))and excellent long-term cycling stability(97%capacitance retention after 3000 cycles)in 1 M Na2SO4 electrolyte.