Effects of dry and wet torrefaction pretreatment on the physicochemical structure of corn stover-derived porous carbon and its performance in supercapacitor applications

Abstract

This study used corn stover as raw materials, employed dry torrefaction and wet torrefaction pretreatment methods combined with KOH activation, and successfully synthesized high-value-added porous carbon materials. Dry torrefaction significantly increased the specific surface area of the porous carbon material to 3657.35 m² g⁻¹ and formed a rich microporous and mesoporous structure, enabling it to exhibit a high specific capacitance of 418.5 F g⁻¹ at a current density of 0.5 A g⁻¹ in a three-electrode system. Wet torrefaction, by increasing the ash removal rate, enhancing the relative crystallinity of the porous carbon precursor, and improving thermal stability, significantly reduced the charge transfer resistance (R_ct = 0.02 Ω). Despite the lower specific surface area (2143.70 m² g⁻¹), it achieved a specific capacitance of 71.0 F g⁻¹ at a current density of 0.5 A g⁻¹ in a two-electrode system and a capacitance retention rate of 101.17 % after 25,000 cycles, demonstrating excellent cycling stability. Therefore, using dry and wet torrefaction pretreatment methods to regulate the structure and surface chemical properties of corn stover-based porous carbon demonstrates the great potential of corn stover as high-performance, low-cost electrode materials for supercapacitors.