Integrated pyrolysis approach of self-O-doped hierarchical porous carbon from yellow mangosteen fruit for excellent solid-state supercapacitor volumetric performance

A recent approach to developing excellent electrode materials with high volumetric capacitance without sacrificing gravimetric capacitance is very challenging for biomass-based porous carbon materials in the practical applications of solid-state supercapacitors. This indicates that the effectiveness of micro-supercapacitors significantly depends on the behavior of 2D3D nanostructures, hydrophilicity, and packing density. Therefore, this research aims to boost the gravimetric-volumetric performances of supercapacitors by preparing biomass-based self-O-doped hierarchical porous carbon nanofiber-nanosheet. The carbon source is focused on the aromatic spices biomass from Indonesia's evergreen yellow mangosteen fruit. The strategy adopted was relatively benign, easy, and simple in the impregnation of ZnCl2 by integrated pyrolysis carbonization-physical activation. The micro-capacitors are designed in a coin compact free-binder synthetic electrode material at an optimum density. The porous carbon obtained possessed a neatly structured morphology in the combination of 3D hierarchical and 2D nanofiber-nanosheet. The results showed that precursor compact design density ranges from 0.991 to 1.41 g cm−3 with a high carbon fixed of 94 % at a functional self‑oxygen doped of 4.2–5.5 %. Furthermore, the optimized porous carbon exhibits a specific surface area of 858.945 m2 g−1 flooded with 89 % micropores. These features contribute to a high gravimetric capacitance of 217 F g−1 with a maximum enhanced volumetric capacitance of 307 F cm−3 at 1 A g−1. In a symmetric supercapacitor system, the gravimetric energy density is marked as 23.45 Wh kg−1 at the highest power density of 1.701 kW kg−1 with an excellent volumetric energy and power densities of 27.7 Wh L−1 and 2.6416 kW L−1, respectively in aqueous electrolyte 1 M H2SO4. These indicate that the yellow mangosteen fruit-based porous carbon with excellent behavior has great potential as a compact coin electrode source for applications in practical, green, and sustainable micro-supercapacitor.