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 KNO₃activation 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 KNO₃activation, the material has a moderate specific surface area (1073.4 m²g^-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^-1at 0.5 A g^-1) and outstanding cyclic stability (capacitance retention reaching 98.3% at 10 A g^-1after 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 Na₂SO₄(15.60 Wh kg^-1), highlighting the potential of this material for energy storage applications.

Keywords: pore structure; pre-carbonization temperature; sesame residue; supercapacitors.