Urea-Predoped, KOH-Activated, Corn Stover–Derived Carbon for CO2 Adsorption

The rising concentration of greenhouse gases causes severe global warming, creating an urgent need for efficient and low-cost carbon dioxide (CO 2 ) adsorption technologies. Corn stover is an abundant agricultural waste that is often underutilized, leading to resource waste and environmental pollution. To develop value-added utilization of this material, corn stover−derived activated carbon is prepared via urea predoping and controlled potassium hydroxide (KOH) etching, while the effects of pyrolysis temperature, urea doping ratio, KOH dosage, and activation temperature are investigated. Under pure CO 2 at 25°C, the optimal adsorbent exhibits an equilibrium CO 2 adsorption capacity of 3.57 mmol·g −1 . Under pure CO 2 at 0°C, the equilibrium capacity increases to 5.91 mmol·g −1 , indicating that lower temperature favors CO 2 physical adsorption. Under a typical flue gas composition of 20% CO 2 /80% N 2 at 25°C, the adsorbent achieves a CO 2 uptake of 1.78 mmol·g −1 after 50 min. The adsorbent exhibits an ideal adsorbed solution theory CO 2 /N 2 selectivity of 30.92. The isosteric heat of adsorption ranges from 28.42 to 23.75 kJ·mol −1 . These values suggest predominantly physical adsorption on heterogeneous sites associated with nitrogen functionalities and structural defects. This study offers insights into the design of biomass-derived CO 2 adsorbents based on corn stover. Graphical Corn stover–derived activated carbon is prepared through urea predoping followed by KOH activation. Nitrogen functionalization and pore development provide complementary contributions to CO 2 capture. The optimized sample reaches 3.57 mmol·g −1 at 25°C and 5.91 mmol·g −1 at 0°C under pure CO 2 , and 1.78 mmol·g −1 after 50 min under simulated flue gas, with an ideal adsorbed solution theory CO 2 /N 2 selectivity of 30.92.