Microwave/freeze casting assisted fabrication of carbon frameworks derived from embedded upholder in tremella for superior performance supercapacitors

Abstract

Three-dimensional squamous hierarchical porous self-supporting carbon frameworks (SSCF) with abundant heteroatoms are prepared through a versatile method combining both the microwave pre-treatment and freeze casting. The microwave and freeze casting treatment promote the formation of ordered pore structures by enhancing the uniform dispersion of KOH within the biomass materials and efficiently avoid the re-aggregation of tremella cell walls. The SSCF has a large accessible surface area (884.1 m2/g) induced by two-dimensional interconnected hierarchical porous carbon nanosheets (IPC1-0.25 activated by appropriate KOH dosage (mtremella:mKOH = 1:0.25)), which is beneficial for abundant ion storage and fast ion transfer. In addition to the electrostatic adsorption, the doped heteroatoms also can provide the faradic contribution. The IPC1-0.25 showed a high specific capacitance of 585.1 F/g and 401.1 F/g at a current density of 0.2 and 1 A/g in 2 M H2SO4, respectively. A record aqueous energy density for biomass carbonous materials of 34.3 W h/kg at the power density of 140 W/kg was verified in 2 M Li2SO4 (pH = 1.8) electrolyte. This work provides an environmentally benign and effective approach for the development of a high-capacitive sustainable biomass carbon-based electrode material.