Tailoring mesoporous and macroporous structures in activated carbon from NaOH-pretreated oak for superior supercapacitors

Abstract

The growing need for sustainable and efficient energy storage solutions has intensified research efforts into eco-friendly materials such as activated carbon (AC) derived from lignocellulosic biomass. Herein, we present a method to enhance the physical characteristics of AC from oak via NaOH pretreatment. The NaOH-pretreated oak was converted into AC through carbonization and chemical activation using KOH as the activating agent. The AC tended to develop mesopores (2–50 nm) and macropores (> 50 nm) as the pretreatment ratio increased (0 %, 1 %, 2 %, and 8 %), achieving a specific surface area of up to 2706 m² g⁻¹ and a pore volume of up to 1.97 cm³ g⁻¹. This result is due to the transformation of the structure of lignocellulosic biomass into a more advantageous structure for pore development through the reactions of delignification and deacetylation that occur during NaOH pretreatment. The mesoporous and macroporous structures offer efficient ion diffusion pathways and reduce resistance, which leads to superior rate capability, capacity retention, and a gravimetric specific capacitance of 44.5 F g⁻¹ at a current density of 1 mA cm⁻² in supercapacitors. The maximum energy and power densities achieved were 45.1 Wh kg⁻¹ and 16.4 kW kg⁻¹, respectively. These results underscore the potential of NaOH-pretreated oak as a sustainable and effective precursor for high-performance AC in energy storage applications, offering new insights into the optimization of the material properties for supercapacitors.