Ionothermal synthesis of microporous and mesoporous carbon aerogels from fructose as electrode materials for supercapacitors

Abstract

The fabrication of hierarchical porous carbons with super-high surface areas from sustainable biomass is still challenging. Silica nanocasting and KOH activation are amenable to porosity introduction and therefore remain the most crucial pathways for porous carbon synthesis. However, these methods are multistep and rather energy-intensive processes. In the present work, a series of hierarchical porous carbon monoliths were prepared from fructose by a one-step ionothermal carbonization approach using an iron-based ionic liquid as solvent, and a porogenic agent. Importantly, the prepared carbon materials show narrow bi-modal pore distributions and possess super-high surface areas of ca. 1200 m² g⁻¹, which is the highest value in hydrothermal carbons as far as we know. The morphology of the monolithic carbons consists of interconnected carbon particles with fairly small particle sizes of ca. 30–50 nm. Moreover, the spent ionic liquids could be easily recovered by Soxhlet extraction, at above 98% for the cycle of ionothermal carbonization. Owing to their favorable textural properties, the impact of the porosity of the ionothermal carbons on their electrochemical capacitive performance was investigated. The ionothermal carbons exhibit a high specific capacitance of 245 F g⁻¹ at a current density of 1 A g⁻¹. The promising capacitive performance could be attributed to the high surface areas and well-controlled micro- and mesoporosities of the carbons. In addition, the hierarchical porosity and high surface area of the carbon lend it to highly efficient adsorption of methyl orange (q_e = 240 mg g⁻¹) and malachite green (q_e = 170 mg g⁻¹) from wastewater.