Optimizing pre-carbonization temperature of sesame residue for hierarchical porous carbon materials in high-performance supercapacitor applications

Abstract In this paper, the sesame residue, a common biomass waste, was used as a precursor to synthesize N,O co-doped porous carbon materials via a simple pre-carbonization and KNO 3 activation two-step strategy. The apparent morphology and supercapacitor performance of the obtained materials can be regulated by changing the pre-carbonization temperature (0 °C, 300 °C and 600 °C). The consequences demonstrate that a large number of C−C and C−O bonds in sesame residue undergo cleavage and form abundant pore structure at the pre-carbonization temperature of 300 °C. After KNO 3 activation, the material has a moderate specific surface area (1073.4 m 2 g −1 ) and affluent heteroatom content (N: 7.52 at%, O: 17.65 at%). As a result, the SS-300 electrode displays exceptional capacitive performance (specific capacitance up to 312.7 F g −1 at 0.5 A g −1 ) and outstanding cyclic stability (capacitance retention reaching 98.3% at 10 A g −1 after 8000 charge–discharge cycles). Moreover, the symmetric supercapacitor assembled by SS-300 exhibits high energy densities in both 6 M KOH (4.58 Wh kg −1 ) and 1 M Na 2 SO 4 (15.60 Wh kg −1 ), highlighting the potential of this material for energy storage applications.