Functionalized nanoporous biocarbon derived from garlic waste for enhanced CO2 capture and supercapacitor performance

Nanoporous activated biocarbons derived from biomass offer a sustainable alternative to traditional carbon materials in various applications. Even though multiple methods are available to prepare these carbon materials with different biomasses and activating agents, there are still many challenges such as optimizing pore structure, surface functionalization control, and maintaining high electrical conductivity which are critical to achieve high performance in energy storage applications. These challenges can be overcome by choosing the appropriate biomass with different chemical structure and composition. Herein, we use food waste garlic to synthesize nanoporous biocarbon through the activation process using potassium hydroxide (KOH) as an activating agent. The resulting biocarbon exhibited a high specific surface area of 3449.2 m² g⁻¹ and a pore volume of 1.67 cm³ g⁻¹, together with sulfur and oxygen functionalities. Pyrolysis was employed to fine-tune the pore structure, achieving a balance of microporosity and mesoporosity, which are beneficial for energy storage and carbon capture applications. The nanostructured materials delivered exceptional CO₂ adsorption capacity at low (5.25 mmol/g at 1 bar) and high pressure (30.6 and 24.9 mmol/g at 0 and 25 °C at 30 bar), making it a promising sorbent for both post-combustion and pre-combustion CO₂ capture. The breakthrough studies combined with the dynamic adsorption models like the Yoon-Nelson and Thomas models demonstrated superior CO₂ capture and rate constant for practical applications. Furthermore, the biocarbon revealed excellent electrochemical performance as a supercapacitor electrode with a specific capacitance of 262 F/g at 0.5 A g⁻¹ and stability over 10,000 cycles with excellent retention and coulombic efficiency. The presence of oxygen and sulfur functionalities enhanced hydrophilicity and wettability, contributing to the superior electrochemical performance. The study highlights the potential of functionalized nanoporous biocarbon with a tunable porous structure derived from waste biomass as a sustainable and efficient material for CO₂ capture and energy storage applications.