Almond skin derived porous biocarbon nanoarchitectonics with tunable micro and mesoporosity for CO2 adsorption and supercapacitors

Abstract

The careful selection of carbon precursors for chemical activation is critical in obtaining cost-effective and efficient porous activated biocarbons with multifunctional properties. Herein, we report on utilising almond skin to synthesize porous activated biocarbons via solid-state KOH activation. Through precise manipulation of the impregnation ratio of KOH to the non-porous carbon, a range of materials with intriguing properties including high surface area, large pore volume, tunable micro and mesopores, and surface functionalization with oxygen were synthesized. The optimized material ASPC5-4 displayed an extremely high surface area (3535 m² g⁻¹), a large pore volume (1.9 cm³ g⁻¹), a high proportion of mesopores (96.5 %) and a notable surface oxygen content (6.93 wt %). These excellent features allowed ASPC5-4 to adsorb a record amount of CO₂ at 0 °C/30 bar (39.81 mmol g⁻¹). Another material ASPC5-2 exhibited a high content of micropores and adsorbed 5.92 mmol g⁻¹ of CO₂ at 0 °C/1 bar. ASPC5-4 also exhibited great potential as a supercapacitor electrode, displaying a high specific capacitance in both a three-electrode (354 F g⁻¹/0.5 A g⁻¹) and two-electrode (203 F g⁻¹/0.5 A g⁻¹) systems. It also demonstrated high power and energy densities of 638 W kg⁻¹ and 47 W h kg⁻¹, respectively.