Waste fruit grain orange–derived 3D hierarchically porous carbon for high-performance all-solid-state supercapacitor

Utilizing renewable and abundant biomass waste to prepare hierarchically porous carbons (HPC) materials with large surface area and good electrical conductivity have received considerable attention recently. In this work, a novel 3D HPC was prepared by a low-cost and facile hydrothermal process, carbonization, and chemical activation from Huiyuan® fruit grain orange (FGO) with expired deadline for the first time. The obtained HPC exhibits a high specific surface area of 2149 m² g⁻¹ and facilitated charge transfer ability offered by its hierarchical structure. When used as electrodes for supercapacitor, HPC displays a maximum specific capacitance of 452.7 F g⁻¹ at 1 A g⁻¹ in 1 M H₂SO₄, which is one of the highest values reported for biomass-derived carbons. Remarkably, the all-solid-state symmetric supercapacitor based on HPC-4 exhibits a high energy density of 14.1 Wh kg⁻¹ at a power density of 140 W kg⁻¹ and outstanding cycling stability (90% capacitance retention after 6000 charge/discharge cycles at 10 A g⁻¹). HPC-4 should be a promising electrode material for all-solid-state supercapacitor application.